the University of Kansas Science Bulletin volume 51, no. 26. pp. 717-801 June 30, 1980 Cytotaxonomy of the Lygaeidae ( Hemipt er a-Het er opt era ) by N. Ueshima and P.D. Ashlock UNI 8121+ :•:•:•:•:•:•:•:•:•:•:■ '.•.•.•.•.•.•.•.•.•••.•».•:•:•:•:• '.•.•-•.•.•.•.•.•.•.•.•.•.•.•.' .•-•.•-•_••••_« ».•.•.••...•.■ •:•:•:•:•:•-•:• THE UNIVERSITY OF KANSAS SCIENCE BULLETIN CYTOTAXONOMY OF THE LYGAEIDAE (HEMIPTERA-HETEROPTERA) I 8 i 1 i I By Norihiro Ueshima and Peter D. Ashlock II I ! g 1 5* Vol. 51, No. 26, pp. 717-801 June 30, 1980 ANNOUNCEMENT The University of Kansas Science Bulletin (continuation of the Kansas Uni- versity Quarterly) is an outlet for scholarly scientific investigations carried out at the University of Kansas or by University faculty and students. Since its incep- tion, volumes of the Bulletin have been variously issued as single bound volumes, as two or three multi-paper parts or as series of individual papers. 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All communications regarding exchanges, sales and subscriptions should be addressed to the Exchange Librarian, University of Kansas Libraries, Lawrence, Kansas 66045. Reprints of individual papers for personal use by investigators are available gratis for most recent and many older issues of the Bulletin. Such requests should be directed to the author. The International Standard Serial Number of this pub'ication is US ISSN 0022-8850. Editor William L. Bloom Editorial Board Philip W. Hedrick Rudolf Jander Harvey Lillywhite Charles D. Michener Norman A. Slade Henry D. Stone George W. Byers, Chairman THE UNIVERSITY OF KANSAS SCIENCE BULLETIN Vol. 51, No. 26, pp. 717-801 June 30, 1980 Cytotaxonomy of the Lygaeidae (Hemiptera - Heteroptera)1 NORIHIRO UESHIMA Department of Biology, Matsusaka College, Kubo-Cho, Matsusaka-shi, Mie, Japan 515 Peter D. Ashlock Department of Entomology, University of Kansas, Lawrence, Kansas 66045 CONTENTS Abstract 717 Introduction - 717 Materials and Methods 720 Cytological Characteristics of the Lygaeidae 721 Lygaeinae 72 1 Orsillinae 726 Metrargini 727 Nysiini 732 Orsillini 734 Ischnorhynchinae 734 Cyminae 737 Cymini 737 Ontiscini 739 Ninini 739 Chauliopinae 739 Blissinae 740 Henestarinae 746 Geocorinae 746 Oxycareninae 749 Pachygronthinae 75 1 Pachygronthini 75 1 Teracriini 752 Heterogastrinae 754 Rhyparochrominae 755 Plinthisini 755 Lethaeini 757 Ozophorini 760 Antillocorini 760 Targaremini _ 762 Drymini 763 Stygnocorini 765 Cleradini 767 Myodochini 767 Udeocorini 771 Rhyparochromini 773 Megalonotini 777 Gonianotini 777 Incertae Sedis 779 Systematic and Cytological Discussion 779 Holokinetic chromosomes 780 Chromosome number 780 Chromosome size 781 The sex chromosome mechanism 783 The m-chromosome 785 Metaphase position of the sex and m-chromosome 785 Species and subspecies discrimination 787 Literature Cited 789 Figures Figures 1-12. Chromosomes of Lygaeinae .... Abstract Chromosomal complements of 330 species of Lygaeidae in 131 genera and 12 subfamilies are discussed. Chromosome numbers and sizes, sex and m-chromosome characteristics including their metaphase positions, and the use of cytological data in discrimination of higher taxa, species, and subspecies are covered. No cy- tological element of the Lygaeidae is unique to the family nor to any part of the family, but several taxa may be characterized by combinations of cytological features. Introduction This survey of the chromosomes of the Lygaeidae was begun early in the 1960s at the University of California, Berkeley, to see whether information pertinent to the classification of the family might be found. Accumulation of data has con- tinued, in Japan by Ueshima, who is re- sponsible for the cytological work and its Contribution number 1700 from the Depart- ment of Entomology, University of Kansas, Law- rence, Kansas 66045. 718 The University of Kansas Science Bulletin interpretation, and in Hawaii and Kansas by Ashlock, who collected and identified many of the specimens and has provided the systematic interpretation. The work has been furthered by several colleagues who sent specimens from various parts of the world. Work on lygaeid chromosomes was be- gun early in the 1900s in the United States by Montgomery (190k, \90U, 1906) and Wilson (1905a, 1905£, 1909, 1912). The most comprehensive contribution was that of Pfaler-Collander (1941), who studied over 50 Finnish species of the family. Other workers in various parts of the world each have added a few to bring the total of cytologically known species to about 75. We here add more than 250 spe- cies to the list. The chromosomes of well over 10% of the 2,800 species listed in Slater's Catalogue of the Lygaeidae of the World (1964) have now been studied. Chromosomes of Lygaeidae, like those of all Hemiptera (Heteroptera and Ho- moptera), are holokinetic; that is, they have diffuse or holocentric centromeres rather than localized centromeres as do most organisms. Because the centromere is distributed along the length of each chromosome, the parts of a fragmented chromosome are not lost and may still move to the poles at anaphase. Another unusual feature found in most Lygaeidae and in some other families of the Heterop- tera is the micro- or m-chromosome. Usu- ally minute, these chromosomes are al- ways unpaired during meiotic prophase and no chiasmata are formed. During the first and second anaphase, they are nega- tively heteropycnotic. Generally, m-chro- mosomes orient themselves in the center of the ring of autosomes at metaphase I and often at metaphase II as well, with the sex chromosomes. The cytogenetic sig- nificance of the m-chromosome is un- known. The chromosomes of spermatogenesis, being the most informative and easiest to obtain, are used in this study. Those of one member of each genus studied are illustrated. Where significant differences were found within a single genus, these differences are also illustrated. Illustra- tions include spermatogonial metaphase and metaphases I and II of meiosis, mostly from a polar view. Occasionally only a lateral view is shown because a suitable polar view was not found in the prepara- tions. Sometimes both lateral and polar views are given, and occasionally other stages of spermatogenesis are shown where these stages show significant additional information. The authors would like this survey to be useful to the cytologist and the He- miptera systematist alike. The materials and methods section thus includes de- scriptions of the process of obtaining and preparing chromosomes for study so that noncytologists who are so inclined may make their own observations. Terms that may not be familiar to the noncytologist are defined below. The actual data is pre- sented by subfamilies with genera grouped alphabetically after a general description of the cytological characteristics of the appropriate subfamily (or tribe in the large subfamily Rhyparochrominae). A summary of the cytological and systematic findings concludes the text of the paper. Tables 1 through 8 compare chromosome sizes of species in well-studied genera. Table 9 gives the modal number for each of the major taxa above the genus level and the positions of the sex chromosomes and m-chromosomes during metaphases I and II. Table 10 lists every species stud- ied to date in the Lygaeidae, the source of information, where the specimens were obtained, and the spermatogonial and metaphase I and II chromosome comple- ments by number. Ueshima (1979) has summarized heteropterous cytogenetics. His summary Cytotaxonomy of Lygaeidae 719 includes a detailed description of meiosis in Oncopeltus fasciatus (Dallas) (Lygaei- dae, Lygaeinae) as well as discussions of holocentric chromosomes, m-chromosomes, the behavior and mechanism of the sex chromosomes, and a list of the diploid and haploid chromosome numbers of all Het- teroptera studied to date. As such, it is a companion to this contribution, and should be consulted for further information on hemipteran cytogenetics. Hemiptera have the usual stages in spermatogenesis. A spermatogonial divi- sion, which is like a typical mitotic divi- sion, is followed by two meiotic divisions. The stages in each division are typical of animals in general. Interphase is the "resting" stage, when the nuclear mem- brane is well defined and the chromosomes are not visible. This is followed by pro- phase, in which the chromosomes con- dense, become visible, and move toward the equatorial plate. At metaphase the chromosomes group on the equatorial plate, the autosomes typically forming a ring around the sex and m-chromosomes. In anaphase the chromosomes travel to the poles, and at telophase the nuclear membrane becomes visible again, and the cell divides in two. In the Heteroptera, the segregation of the autosomes is reduc- tional (see below) during the first meiot- ic division and the segregation of the sex chromosome is equational. During the second division, the autosomes divide equationally and the sex chromosomes di- vide reductionally. There is no interphase between the first and second meiotic divi- sions in the Heteroptera. The definitions that follow are of terms that may be less familiar to some readers. dia\inesis — stage during meiotic prophase in which chromosome contraction is near maximum (Fig. 3c). diffuse stage — stage preceding diplotene during prophase in which the autosomes are not visible as discrete structures al- though the sex chromosomes may be dis- cernible. The diffuse stage is character- istic of the Heteroptera (Fig. 6b). diplotene — stage during prophase in which chiasmata may be evident in each pair of homologous chromosomes (Fig. 3b). equational division — the segregation pat- tern in which sister chromatids of a chromosome segregate to opposite poles (see reductional). heteropyenotic — chromosomes or chromo- some regions that stain differently from the rest of the genome. Positive hetero- pyenosis refers to darker staining ele- ments, negative heteropyenosis to lighter staining elements. isopyenotic — chromosomes or chromo- some regions that stain the same as the majority of the euchromatin, i.e., are not heteropyenotic. reductional division — the segregation pat- tern in which sister chromatids of a chromosome (e.g., the paternal chromo- some) remain together and proceed to one pole while the chromatids of the homologous chromosome (e.g., the ma- ternal chromosome) segregate to the other pole (see equational). Acknowledgments We would like to acknowledge the great number of specimens sent to us by J. A. Slater and his group (including Merrill H. Sweet, Randall T. Schuh, and Samuel Sla- ter), who collected in South Africa in 1967- 68 and who also collected in Florida (with Jane E. Harrington), and in Connecticut. Many specimens from Central Africa (Tan- zania) were provided by G. G. E. Scudder. Some orsillines and other lygaeids from New Zealand were provided by A. C. Eyles. Ue- shima collected material in Fiji, New Cale- donia, and Malaysia while supported by U.S. Public Health Grant GM-13197 to R. L. Usinger, and he completed his part of this work at the University of Kansas in Law- rence, supported by a grant from the Matsu- 720 The University of Kansas Science Bulletin saka College. Ashlock collected specimens in California and North Carolina, and dur- ing four years at the Bishop Museum in Honolulu he collected on all of the major islands of Hawaii and for a short period in Japan, aided by National Science Foundation Grants GB-3105 and GB-5860. A U.S.-Japan cooperative grant from N.S.F. resulted in six weeks of collecting in Laos and Thailand by Ashlock in the same period. Steven Hamil- ton, Alex Slater, and Virginia Ashlock have read the manscript and corrected many errors. Materials and Methods About 35 taxa listed herein are un- identified to species, sometimes because they are undescribed. Those from Thai- land were collected by Ashlock (PDA). Those from Malaysia were collected by Ueshima (MLY). Those from South Af- rica were collected by J. A. Slater and his group, those from Tanzania by G. G. E. Scudder (GGES). Some of these speci- mens have been lost; all others are in the collector's collection or in the Bishop Mu- seum, Honolulu, except those of Ueshima, which are with Ashlock. These specimens are identified with a code number, the collector code, or both. Hopefully those extant specimens with code numbers can be identified and /or named in the future. Specimens used in this study were mostly field collected, preserved in isopro- pyl Carnoy's fixative (Ueshima, 1963) or standard Carnoy's fixative, and prepared with the standard or quick squash tech- nique. All observations were made with the aid of a camera lucida and photo- graphs were taken with a 35-mm camera. Magnifications are indicated by a 10-/mi scale on each drawing. The above description is sufficient for those familiar with cytological techniques, but since hopefully this paper will be used by workers with little or no cytological training who may wish to study insect chromosomes, the following instructions are included. Squash Technique for Chromosome Study Specimens for study must be in active spermatogenesis or oogenesis. The time when this occurs differs from group to group. In lygaeids and Hemiptera in gen- eral, adults that have just gained their full color are the most suitable. Other insects may be at the best stage during the last nymphal instars or as pupae or teneral adults. Field-collected specimens are killed and preserved in either standard or iso- propyl Carnoy's fixative. They may be held for chromosome study in either fixa- tive or they may be transferred to 70% ethyl alcohol. In an emergency, specimens may be preserved in 70%, or better, 98% isopropyl alcohol, though the fixation and resulting chromosome preparation will be less satisfactory. Males are far more pro- ductive for study: only in males can the details of sex determination be studied, and far more sperm than eggs are pro- duced so that the chance of finding di- viding cells is greater. Standard technique.— \. Dissect out the testes or ovaries in fixative. In small speci- mens, gonads may be dissected out after the whole specimen is fixed. 2. Fix testes or ovaries in isopropyl or standard Car- noy's fixative for 24 hours or more. 3. Place in acetocarmine stain for about 24 hours. 4. Remove gonads from stain and place on a glass slide. Add a few drops of stain and apply a coverslip. 5. Tap and press lightly on coverslip with forceps, be- ing careful not to move it. Place a piece of filter paper over the coverslip and press gently with fingers to squash specimen, again being careful not to move the cover- slip. Blot up excess stain. The prepara- tion is now ready for study. If overstained, destain with 45% acetic acid. 6. To make the preparation last for several months, seal the edges of the coverslip with a paraf- fin-balsam mixture. To make the prepara- tion permanent, freeze it for about 10 min- utes using dry ice, or for a few seconds Cytotaxonomy of Lygaeidae 721 with liquid nitrogen. Then very quickly remove the coverslip with a sharp razor blade, air dry the slide for 1 minute, add Euparol, and replace the coverslip. Ouicf{ technique. — This method is much faster, but it does not yield as good a preparation and is much less satisfactory for obtaining photographs. 1. As in stand- ard technique. 2. Fix testes or ovaries in isopropyl or standard Carnoy's fixative for 15 minutes. 3. Place gonads on glass slide and add a few drops of acetocarmine stain. Warm slide gently under a desk lamp and as the stain evaporates add more, taking care that the specimen does not become dry. Continue for 15 minutes. 4. Blot up as much stain as possible from around specimen with filter paper, wash with more stain, and blot again. 5. As in stand- ard technique. 6. As in standard tech- nique. Reagents for chromosome study. — 1. Isopropyl Carnoy's fixative: 1 part glacial acetic acid to 3 parts isopropyl alcohol, 98% to pure. This fixative may be kept for more than three months without losing its effectiveness. 2. Carnoy's fixative (standard) : 1 part glacial acetic acid to 3 parts ethyl alcohol, 95%. This fixative may be used in place of the isopropyl Carnoy's, but many cytologists feel that it must be used within two days after mixing. 3. Acetocarmine stain. Dissolve 1 gram basic carmine into 100 ml 45% acetic acid. Boil 20 to 30 minutes, but do not evaporate. Use of a condenser placed vertically over the boiling flask is recommended. Filter. Aceto-orcein stain is preferred by many, but pure orcein must be used. One gram orcein is dissolved in 100 ml 45% acetic acid and allowed to stand for 3 to 4 days. Filter. 4. Acetocarmine stain (modified for quick technique). To about 10 ml of acetocarmine stain add 4 or 5 drops of ferric acetate saturated in propionic acid. Let the stain mixture stand for at least 1 hour before use. 5. Paraffin-balsam mix- ture: 1 part paraffin (60° C or higher melting point) to 1 part balsam (as pre- pared to mount tissues). Boil together for about 20 minutes and allow to solidify. The mixture can be applied with a heated spatula. Cytological Characteristics of the Lygaeidae Lygaeinae The chromosome cytology of 12 gen- era and 26 species of the subfamily Ly- gaeinae has been studied. The great ma- jority have 14 (12 + XY) chromosomes, only one genus, Oncopeltus, diverging much from that number. Therefore, it is safe to assume that the modal number for the subfamily is 14 (12 + XY). The gen- era Lygaeus and Oncopeltus each have one species (L. simlus and O. famelicus) with 22 (20 + XY). This unusually high number may be derived either by simple fragmentation of some chromosomes as in the genus Thyanta (Schrader and Hughes- Schrader, 1956) or by chromosome auton- omy as in Banasa (Schrader and Hughes- Schrader, 1958). A characteristic of the subfamily is the lack of an m-chromosome. This situation is found elsewhere only in the Oxycareni- nae and a few genera of the Rhyparochro- minae. The behavior of sex chromosomes during meiosis in this subfamily is quite orthodox in Heteroptera. At metaphase I and II, the X and Y chromosomes lie in the center of a ring formed by the auto- somes. Figure 132 shows the distribution pattern of the chromosome complement in this subfamily. 1. Arocatus rusticus (Stal). — The male diploid chromosome complement in Aro- catus rusticus consists of six pairs of auto- somes and an XY sex pair. All the chro- mosomes except the Y are medium-sized (Fig. la). The Y chromosome is about half as large as the others and so is easily distinguished. 722 The University of Kansas Science Bulletin II • • rusticus suboeneus t t ^ 1 • t • c t Lygaeinae Arocatus 0$K a 2 Arocatus U :i :V •? .'V <:, J i; ..■.■5»:--'.:-. >:; 1' t, V; ''•■"v. -V '.'• J*/ 1 « .V ■■:>< Vjfr .-": . ■- .' b J/ e II • * i c •!•.' ft *' 3 Graptost< ;thus manillensis t»«j«;i #•#• ^••f %••;$ 4 Lygaeosp ilus tripunctatus a A . b 1 f ;V 5 Lygaeus kalmii Fig. 1-5. Chromosomes of named species of Lygaeinae: a, spermatogonial metaphase; b, first metaphase; c, second metaphase. (Exception Fig. 3: b, diplotene; c, diakinesis; d, first metaphase; e, second metaphase; f, second anaphase.) Scale zz 10 /xm. Cytotaxonomy of Lygaeidae 723 The male meiosis of this species is typical of Heteroptera in general. The sex chromosomes, X and Y, are positively heteropycnotic in early prophase. In the diffuse stage, the X and Y tend to undergo nonhomologous association, which seems to persist into early diakinesis. Rapidly after the diffuse stage, the tetrad nature oi the six bivalents reappears, the bivalents are usually characterized by one chaisma, and they pass into a typical diakinesis. By late diakinesis, the X and Y separate from each other, become isopycnotic, and can be resolved as double structures composed of two sister chromatids. The terminaliza- tion of chiasmata is completed by the first metaphase. At the first metaphase, six autosomal bivalents have oriented on the periphery of a hollow spindle, while the X and Y univalents invariably lie side by side and occupy the center of the spindle formed by the autosomes (Fig. lb). The first division of meiosis is reductional for the autosomes and equational for the sex chromosomes. As is usual in Heteroptera, the second meiosis follows directly from telophase I without any interphase. At the second metaphase, the autosomes again form a hollow spindle and lie on the pe- riphery while the X and Y again occupy the center of a spindle and undergo the characteristic "touch and go" pairing (Fig. lc). During anaphase II, the X and Y pass to opposite poles with the autosome haves. 2. Arocatus suboeneus Montandon. — The chromosome number of Arocatus sub- oeneus is 15 in the diploid male, consist- ing of 12 autosomes and X1X2Y sex chro- mosomes (Fig. 2a). All autosomes are similar in size and the Xi is as large as the autosomes. The X2 and Y are less than half the size of the autosomes. Be- cause they are the same size, they are indistinguishable from one another. The course of meiosis (Fig. 2b, c) is the same as in A. rusticus. In the second anaphase, the Xi and X2 go to one pole while the Y moves to the other. 3. Graptostethus manillensis (Stal). — The male chromosome complement of Graptostethus manillensis is six pairs of autosomes plus an XY pair (Fig. 3a). Two pairs of autosomes are somewhat larger than the other four pairs. The X chromosome is the same size as the small- er autosomes and indistinguishable from them, while the Y is the smallest com- ponent in the chromosome set and easily distinguished. The course of meiosis is the same as in Arocatus rusticus. By diakinesis, the X and Y are both positively heteropycnotic. In the diffuse stage, the X and Y come close together and remain so to the late diplotene stage (Fig. 3b). In early dia- kinesis the X and Y separate from each other and may already be seen as double structures (Fig. 3c). With continued con- traction of six autosomal tetrads (biva- lents), the X and Y become isopycnotic in late diakinesis. By the prometaphase, the terminalization of chiasmata on each auto- some is completed. At metaphase I, six autosomal tetrads form a hollow spindle and lie on the periphery of the spindle while the X and Y lie in the center (Fig. 3d). During ana- phase I, the X and Y divide equationally. At metaphase II, the autosomes again lie on the periphery of a spindle and the X and Y occupy the center of the spindle with the characteristic "touch and go" pairing (Fig. 3e). In anaphase II, the X and Y separate to opposite poles with the autosomes (Fig. 3f). 4. Lvgaeospilus tnpunctatus (Dallas). — The chromosome complement of Lvgaeo- spilus tripunctatus is six pairs of autosomes and an XY pair. Two of the six pairs of autosomes are slightly larger than the others and the Y is the smallest component in the set, while the X belongs to the intermediate group in size and cannot be 724 The University of Kansas Science Bulletin distinguished from the autosomes (Fig. 4a). The meiotic process of this species (Fig. 4b, c) is the same as in the foregoing species in every respect. 5. Lygaeits kalmii Stal. — The diploid metaphase of Lygaeus kalmii consists of six pairs of autosomes and an XY pair. The X and Y are not conspicuous since they are similar to the autosomes in size. However, one chromosome, presumably the Y, is slightly smaller than the rest of the chromosomes (Fig. 5a). The course of meiosis (Fig. 5b, c) is the same as in species described previously. 6. Melanopleurus bistriangirfaris (Say) and M. pyrrhopterus melanopleurus (Uh- ler). — The male diploid chromosome complement of both Melanopleurus bistri- angirfaris and M. pyrrhopterus melano- pleurus is six pairs of autosomes and an XY sex chromosome pair (Fig. 6a). In the spermatogonial metaphase of both spe- cies, the X and Y are not easily distin- guished from the autosomes, since all the chromosomes are similar in size. The course of meiosis in these two species is the same as in other species previously described. However, in the diffuse stage of M. bistriangirfaris, posi- tively heteropycnotic X and Y chromo- somes have separated from each other (Fig. 6b) and clearly show the double na- ture of sister chromatids. This double nature at the diffuse stage is not conspicu- ous in other species. The first and second metaphases also proceed as in previously described species (Fig. 6c, d). 7. Melanostethus marginatus (Thun- berg). — The spermatogonial metaphase of Melanostethus marginatus consists of six pairs of autosomes and an XY pair (Fig. 7a). One pair of autosomes is smaller than the others, the X is similar to the small autosomes in size, and the Y is the smallest component in the set. The course of meiosis in the species (Fig. 7b, d) is as in previously described species. The X and Y divide equationally in the first division (Fig. 7c). 8. Neacoryphus bicrucis (Say) and N. rubicollis (Uhler). — The diploid chromo- some complement of Neacoryphus bicrucis and N. rubicollis consists of six pairs of autosomes and an XY sex chromosome pair (Fig. 8a). One of the chromosomes in the set, presumably the Y, is smaller than the others and easily recognized. The meiotic process of these species (Fig. 8b, c) is the same as in preceding species. 9. Ochrimnus tripligatus (Barber). — The diploid chromosome complement of Ochrimnus tripligatus consists of six pairs of autosomes and an XY sex pair (Fig. 9a). In this species the sex chromosomes are easily distinguished from the auto- somes because of their smaller size. One of these sex chromosomes, presumably the Y, is only about half the size of the X. The course of meiosis of the species (Fig. 9b, c) is. like those described previously in every respect. 10. Oncopeltus famelicus (Fabricius). — The spermatogonial metaphase plate of Oncopeltus famelicus consists of ten pairs of autosomes and an XY sex chromosome pair (Fig. 10a). The X and Y are indis- tinguishable from the autosomes because all chromosomes are similar in size. The course of meiosis of the species is quite orthodox (Fig. 10b, c), unaffected by the large number of chromosomes. Of course, the X and Y are equational at the first division. 11. Oncopeltus fasciatus (Dallas). — The details of the spermatogenesis of Oncopel- tus fasciatus have been described by Mont- gomery (1901£, 1906) and Wolfe and John (1965). Our findings for this species con- firm their observations of the chromosome cytology. The chromosome complement of the male diploid set of this species is seven pairs of autosomes plus an XY sex pair (Fig. 11a). All the chromosomes are simi- Cytotaxonomy of Lygaeidae .■ - &- * -s ■&&&$&$ • b .i.W*V' "1 &gM*i$%tik H ttlt 725 Lygaeinae ini;tid 6 Melanopleurus bistriangularis a • it I I I » t • 7 Melanostethus marginatus a ••V 8 Neacoryphus bicrucis V'i1 t • a *2> 9 Ochrimnus tripligatus Oil' »l » »v a 10 Oncopeltus famelicus t • 'I t 1 1 a • • t • • • J Oncopeltus fasciatus *J&* a I ? • b M.Hil 12 Spilostethus ho spes Fig. 6-12. Chromosomes of named species of Lygaeinae: a, spermatogonia! metaphase; b, first metaphase; c, second metaphase. (Exceptions Fig. 6: b, diffuse stage; c, first metaphase; d, second metaphase. Fig. 7: c, first anaphase; d, second metaphase.) Scale = 10 /*m. 726 The University of Kansas Science Bulletin lar in size. The course of meiosis (Fig. lib, c) is as in previously described species. 12. Spilostethus hospes (Fabricius), S. jurculus (H.-Schaeffer), and S. macilentus (Stal). — The spermatogonia! metaphase plates of Spilostethus hospes, S. jurculus, and S. macilentus consist of six pairs of autosomes and an XY sex pair (Fig. 12a). One pair of autosomes is slightly larger than the others. The spermatogenesis of S. hospes (as Lygaeus hospes) has been studied by Manna (1951). Our observa- tions of this species confirm his in every feature. The course of meiosis in these three species (Fig. 12b, c) is the same as in others previously described. Orsillinae In the orsilline tribe Metrargini, seven genera and 31 species are now known cytologically. All genera except Darwin- ysius present 16 (14 + XY) chromosomes. Darwinysius shows 14 (12 + XY) instead of 16. In the genus Neseis, specimens of N. hiloensis approximatus collected from West Maui, Hawaii, had 18 (16 + XY) instead of the 16 found in the one other collection of this species. This 18-chro- mosome form is definitely derived from the 16-chromosome form either by dupli- cation or by fragmentation of one pair of autosomes (see Fig. 132c, d). The modal number of the tribe is 16 (14 + XY). In the Nysiini, four genera and 28 species have been cytologically studied. All species except Nysius tenellus show 14 (12 + XY) chromosomes. There is no doubt that the modal number of the tribe is 14 (12 + XY). All the species with 14 chromosomes always have one pair of extremely large autosomes. This is char- acteristic of the tribe. One of the 21 spe- cies of Nysius examined, N. tenellus, has 22 (20 + XY) chromosomes instead ot 14 (see Fig. 132e, f). This high chromo- some number may be caused by fragmen- tation or chromosome autonomy, possibly because of the holokinetic nature of he- mipterous chromosomes (Schrader and Hughes-Schrader, 1956, 1958). In the Orsillini, two genera and six species have been worked out. The genus Hudsona has 14 (12 + XY) chromosomes (Eyles, pers. comm., informs us that this genus may belong to the Nysiini, how- ever), but the genus Ortholomus shows two chromosome types: 14 (12 + XY) and 16 (14 + XY)'. All Ortholomus spe- cies always have one pair of extremely large autosomes (see Fig. 132h, i). How- ever, the 14-chromosome species also have a pair of large autosomes that are interme- diate in size between the extremely large and medium autosomes. Such an inter- mediate-sized autosome pair does not oc- cur in the species with 16 chromosomes. Therefore it can be assumed that the 16 chromosomes are derived from 14 by the fracture of the intermediate large pairs of autosomes. The modal number of the tribe is assumed to be 14 (12 + XY). The ancestral stock of the subfamily Orsillinae may have had 14 (12 + XY) chromosomes for the following reasons. All species with 14 chromosomes, and the Ortholomus species with 16 chromosomes, invariably show one extremely large pair of autosomes. In the Metrargini, all the species with 16 chromosomes have no such extremely large autosomes and Darwin- ysius species, which show 14 chromosomes and are a primitive genus in the tribe, have a pair of extremely large autosomes. Therefore, the 16-chromosome state in the Metrargini seems to be derived from the 14-chromosome stock by the fracture of one pair of extremely large autosomes. All species in the Nysiini except Nysius tenel- lus have a pair of such extremely large autosomes and have 14 chromosomes. The distributional pattern of the chro- mosome complement in the Orsillinae and comparative size difference of chromo- somes in various groups in the Orsillinae Cytotaxonomy of Lygaeidae 727 are shown in Figures 131 and 133. Other characteristics of chromosome cytology in the Orsillinae are the presence of a pair of m-chromosomes and the cen- tral position of the X, Y, and m-chromo- some at metaphase I. At metaphase II, the XV pseudopair and the m again take a central position in Metrargini. However, in species of the Nysiini and Orsillini, the XY lies in the center and the m-chromo- some tends to locate on the periphery with the autosomes (see Figs. 13-27). Metrargini. 13. Darwinysius marginalis (Dallas) and D. wenmanensis Ashlock. — Darwin- ysius marginalis and D. wenmanensis have the same chromosomal constitution. The male diploid chromosome complements of these species consist of five pairs of auto- somes, a pair of m-chromosomes, and an XY sex pair (Fig. 131a). One autosome pair is very much larger than the others and is easily recognized. The pair of m- chromosomes is the smallest component in the set and is about half the size of the Y chromosome. The X chromosome is about the same size as the medium-sized autosomes and the Y is about half the size of the X. During meiosis, the X and Y chromo- somes are positively heteropycnotic in the early prophase and undergo nonhomolo- gous association. This status of the sex chromosomes seems to persist into the diplotene stage. Immediately after the dif- fuse stage, autosomes become evident, and the X and Y are already double structures composed of sister chromatids. In late diakinesis, the X and Y become isopyc- notic, but they can be distinguished from the autosomes because they are composed of two instead of four chromatids, as are autosomal bivalents. Terminalization of chiasmata on the autosome pair is com- pleted by the prometaphase. The m-chromosomes are unpaired dur- ing prophase and there is no evidence for crossing-over between them. At prometa- phase, the m-chromosomes come close to- gether and at metaphase they are momen- tarily co-oriented at the center of a hollow spindle (Fig. 13b). The m-chromosomes are negatively heteropycnotic at meta- phase I and they maintain this condition until the completion of meiosis. At metaphase I, five autosomal biva- lents have oriented on the periphery of a spindle while the X and Y univalents and the m-chromosome lie side by side and invariably occupy the center (Fig. 13b). The first meiosis is equational for the sex chromosomes but is reductional for the autosomes and the m-chromosome. The second metaphase follows directly upon completion of the first division without any resting period. At metaphase II, the autosomes again lie on the periphery of a spindle while the XY pseudopair and the m-chromosome lie side by side and oc- cupy the center of the spindle (Fig. 13c). The m-chromosome is negatively hetero- pycnotic during the second meiosis. As a result of the second division there are two kinds of spermatids: one containing five autosomes, an m-chromosome, and the X, and another containing five autosomes, an m-chromosome, and the Y. 14. Glvptonysiits hylaeus (Kirkaldy), G. amicola Ashlock, and Glyptonysius sp. from West Maui, Hawaii. — These three Glyptonysius species will be described to- gether since they are the same in essential chromosome cytology. The spermatogonial metaphase consists of six pairs of auto- somes, a pair of the m-chromosomes, and an XY sex pair (Fig. 14a). One of the six pairs of autosomes is slightly larger than the others. The m-chromosomes are the smallest component in the set. In G. amicola, the X chromosome is a little smaller than the small-sized chromosomes, the Y is about half as large as the X, and the m-chromosomes are about half as 728 The University of Kansas Science Bulletin jM & a c ii sb {»»•.•»• Orsillinae METRARGINI m 10 Darwinysius marginalis H Glyptonysius hylaeus ,#«.a _• • b ••• #v yrt ••?•• iiftiiii ..% ;v 15 Metrarga elinguis •••• ••••# ?•'•• *#•• a 16 Neseis kirkaldyi I t b I V I V.1 «. a fit b Aft '-»» * ••'• 17 Neseis hiloensis - from W. Maui • ••• MS a 18 Nesoelimacias contracta f I f *.; i Fig. 13-18. Chromosomes of named species of Orsillinae: a, spermatogonial metaphase; b, first metaphase; c, second metaphase. {Exception Fig. 15: d, second anaphase.) Scale = 10 /*m. Cytotaxonomy of Lygaeidae 729 large as the Y. In G. hylaeus, the X is two-thirds as large as the small-sized auto- somes and about twice as large as the Y, and the m-chromosomes are about half as large as the Y (see Fig. 14a). In Glypto- nysius sp. from West Maui, the X is only slightly smaller than the small-sized auto- somes, the Y is half the size of the X and the m-chromosome is a little smaller than theY. The course of meiosis of these three species (Fig. 14b, c) is the same as in Darwinysius marginalis. The X and Y are positively heteropycnotic in early prophase and become isopycnotic by the prometa- phase. The m-chromosomes are unpaired during the prophase and negatively hetero- pycnotic at the first metaphase. The separation of the first meiosis is reduc- tional for the autosomes and the m-chro- mosome and equational for the sex chro- mosomes. 15. Metrarga elingitis Ashlock. — The diploid chromosome complement of Me- trarga elingitis is six pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 15a). One pair of auto- somes is a little smaller than the others. The X chromosome is a little smaller than the small-sized autosomes, and the Y is about two-thirds as large as the X. The m-chromosomes are about two-thirds as large as the Y. The course of meiosis in this species (Fig. 15b, c) is the same as in Darwin- ysius marginalis. The X and Y are posi- tively heteropycnotic in the early prophase and become isopycnotic by late diakinesis. The m-chromosome is unpaired during the prophase and negatively heteropycnotic at metaphase I. The m-chromosome is, again, negatively heteropycnotic during the second division (Fig. 15c, d). 16. Neseis hjrhaldyi (Usinger) and other Neseis spp. — The chromosome cy- tology of the following species is the same in essential features: Neseis ehinai Using- er; N. jasciata convergens Usinger; N. ful- gida Usinger; N. hiloensis approximata Usinger, from East Maui, Hawaii; N. h. hiloensis (Perkins); N. h. interoculata Usinger; N. h. jugata Usinger; N. sp. near hiloensis; N. /{irl^aldyi (Usinger) ; N. leg- nota Ashlock; N. nitida consummata Usinger; N. n. impressicolis Usinger; N. n. insulicola (Kirkaldy); N. n. nitida (B.- White); N. ochriasis baldwini Usinger; N. o. maculiceps Usinger; N. o. ochriasis (Kirkaldy); N. pallassata Ashlock; N. pallida Usinger; N. saundersiana (Kirk- aldy); and N. silvestrts (Kirkaldy). The male diploid chromosome complement of these species consists of six pairs of auto- somes, a pair of m-chromosomes, and an XY sex pair, as shown in Figure 16a. Comparative differences in chromosome components are listed in Table 1. The meiotic process of these species is as in Darwinysius marginalis. Therefore, the course of meiosis is described using N. kjrkaldy as an example (Fig. 16b, c). The X and Y are positively heteropycnotic in the early prophase and nonhomologously associated at the diffuse stage. By late dia- kinesis the X and Y become isopycnotic. The first division is reductional for the m-chromosome and equational for the sex chromosomes. 17. Neseis hiloensis approximata Using- er from West Maui, Hawaii. — The speci- mens originally identified as Neseis hilo- ensis approximata from West Maui have a different chromosome complement from others of the genus. The diploid chromo- some complement is seven pairs of auto- somes, a pair of m-chromosomes, and an XY sex pair (Fig. 17a). One pair of auto- somes is smaller than the others. The X is the same size as the smaller autosomes, the Y is about half as large as the X, and the m-chromosome is a little smaller than the Y. The course of meiosis of the speci- mens (Fig. 17b, c) is essentially the same 730 The University of Kansas Science Bulletin as in Darwinysius marginalis and in other species of Neseis. These specimens may represent a sibling species of N. hiloensis, but further study is needed to clarify the situation. See fur- ther comments in the discussion section. 18. Nesoclimacias contractu (Black- burn).— The spermatogonial metaphase of Nesoclimacias contractu consists of six pairs of autosomes, an m-chromosome pair, and an XY sex chromosome pair (Fig. 18a). One pair of autosomes is smaller than the others. The X chromosome is about the same size as the small auto- somes, and the Y is about half the size of the X and a little larger than the m- chromosome. The meiotic process of the species (Fig. 18b, c), is the same as in Darwinysius species. 19. Oceamdes bimaculatus Usinger and other Oceanides spp. — All nine species of the genus Oceanides observed have the same chromosome complement. The nine species are Oceanides bimaculatus Usinger, O. dilatipennis Usinger, O. euphorbiae Ashlock, O. fosbergi Usinger, O. gressitti Ashlock, O. montivagus (Kirkaldy), 0. nimbatus (Kirkaldy), O. centralis Usinger, and O. yoshimotoi Ashlock. The diploid chromosome complement of these species consists of six pairs of autosomes, an m- chromosome pair, and the XY sex pair (Fig. 19a). Comparative differences in chromosome complements among the spe- cies are listed in Table 2. The meiotic processes of these nine species are much the same as in Dartvin- ysius. The description of the meiotic proc- ess (Fig. 19b-d) is based on observations of O. bimaculatus as an example. The X and Y are positively heteropycnotic in early prophase and become isopycnotic by late diakinesis. The m-chromosomes are unpaired during the prophase and are negatively heteropycnotic at metaphase I. 20. Xyonysius basalis (Dallas), X. cali- fornicus (Stal), and X. naso (Van Duzee). These three Xyonysius species have the same chromosome constitution. The sper- matogonial metaphase of these species is Table 1. Relative size differences of chromosome complements in the genus Neseis (Orsil- linae) (EL, extra large; L, large; M, medium-sized; S, small). No. autosome pairs Species N. kjrkjildy (Usinger) N. ochriasis balduini Usinger N. o. macithceps Usinger N. o. ochriasis (Kirkaldy) N. pallida Usinger N. chinai Usinger N. jasciata convergent Usinger N. fulgida Usinger N. hiloensis hiloensis (Perkins) N. h. approximata Usinger (E. Maui) N. h. approximata Usinger (W. Maui) N. h. jugata Usinger N. h. interoculata Usinger N. sp. near hiloensis N. legnota Ashlock N. nitida nitida (B. -White) N. n. consummata Usinger N. n. impressicollis Usinger N. n. insulicola (Kirkaldy) N. pallassata Ashlock N. sanndersiana (Kirkaldy) N. silvestris (Kirkaldy) EL M Sex chromosomes X Y 5 5 5 5 5 5 4 5 6 6 6 6 6 6 5 5 5 5 5 5 6 5 1/2Y 2/3Y 1/2Y 1/2Y 1/2Y 2/3Y 2/3Y Y Y 2/3Y 1/2Y 2/3Y 1/2Y 1/2Y 2/3Y 2/3Y 2/3Y 2/3Y 2/3Y 2/3Y 1/2Y 2/3Y S M M M M M S S M M M M M M M M M M M M M S 1/3X 1/3X 1/2X 1/3X 1/2X 1/2X 2/3X 1/2X 2/3X 1/2X 2/3X 2/3X 1/2X 1/2X 1/2X 1/2X 1/2X 1/2X 1/2X 1/3X 1/2X 2/3X Cytotaxonomy of Lycaeidae 731 t Orsillinae f/A & lib | ,, I c METRARGINI #5 I •» I ••, f I • • 19 Oceanides bimaculatus a a b 20 Xyonysius basalis •/# a • • b ft «&• |:M| ill •••• 21 Nesomartis psammophila f i£,a n |. in »v» 22 Nysius abnormis tt c in i I,, I 23 Nysius tenellus #1 , ' « • I ?• 24 Rhypodes clavicornis NYSIINI Fig. 19-24. Chromosomes of named species of Orsillinae: a, spermatogonia! metaphasc; b, first metaphasc; c, second metaphasc (Exception Fig. 19: c and d, second metaphasc.) Scale = 10 /an. 732 The University of Kansas Science Bulletin composed of six pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 20a). In X. basalts, two pairs of autosomes are smaller than the other four. The X chromosome is equal in size to the small autosomes. The Y is about half the size of the X and the m-chromosome is half the size of the Y. In X. calijornicus, only one of the six pairs of autosomes is smaller than the others. The X chromo- some is larger than the small-sized auto- somes but smaller than the medium-sized ones. The Y is slightly smaller than the X and larger than the m. In X. naso, two of the six pairs of autosomes are a little smaller than the others. The X chromo- some is the same size as the small-sized autosomes. The Y is slightly smaller than the X and is twice as large as the m-chro- mosomes. The course of meiosis (Fig. 20b, c) is, in essential features, the same as in Darwin - ysms. The X and Y are positively hetero- pycnotic in early prophase and become isopycnotic in late diakinesis. The m- chromosomes are unpaired during pro- phase and are negatively heteropycnotic at the first metaphase. Nysiini. 21. Nesomartis psammophila Kirkaldy. — The diploid chromosome complement of Nesomartis psammophila consists of five pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 21a). In the spermatogonial metaphase set, one pair of autosomes is very much larger than the others. The X chromosome is smaller than any of the autosomes and is about three times as large as the Y. The m- chromosome is about half the size of the Y. The course of meiosis of this species (Fig. 21b, c) is similar to that of Darwin- ysius marginalis except that the m-chro- mosome lies on the periphery of the spin- dle at metaphase II (Fig. 21c). 22. Nysius abnormis Usinger and other Nysius. spp. — The following 19 species have been observed cytologically and are the same in their chromosome cytology: Nysius abnormis Usinger, N. angustatus Uhler, N . beardsleyi Ashlock, N. caledo- niae Distant, N. coenosulus Stal, N . com- munis Usinger, N. ericae (Schilling) (= N. natalensis Evans), N. jullawayi Using- er, N. huttoni B.-White, N. lichenicola Kirkaldy, N. longicollis Blackburn, N. nemorivag'its B.-White, N. niger Baker, N. raphanus Howard, N. scutellatus Dal- las, N. stali Evans, N. usitatus Ashlock, N. vinitor Bergroth, and Nysius sp. (mix- tus?). The spermatogonial metaphase of these 19 species consists of five pairs of autosomes including one extremely large pair, a pair of m-chromosomes, and an XY sex pair (Fig. 22a). In the metaphase set, the smallest pair invariably is the m-chro- mosome. Comparative differences of size in chromosome constitution of these 19 Table 2. Relative size differences of chromosome complements in the genus Oceamdes (Or- sillinae) (EL, extra large; L, large; M, medium-sized; S, small). Species O. bimaculattis Usinger O. dilatipennis Usinger .... O. citphorbiac Ashlock .... O. josbergi Usinger O. gressitti Ashlock O. montivagits (Kirkaldy) O. nimbatus (Kirkaldy) .. O. ventralis Usinger O. yoshimotoi Ashlock .... No. autosome pairs in Sex chromosomes EL L M X Y 5 5 5 5 5 1 5 5 5 5 1 1 2/3Y I 2/3Y I Y I Y 2/3Y I 2/3Y [ Y I 1/2Y Y M S S S M S S S M 1/2X 2/3X 2/3X 2/3X 1/2X 1/2X 1/2X 1/2X 1/2X Cytotaxonomy of Lygaeidae 733 species are shown in Table 3. For exam- ple, in N. abnormis, the X chromosome is about equal to the small-sized autosomes and is about three times as large as the Y. The m-chromosomes are about half the size of the Y. The meiotic sequence of these 19 spe- cies is the same in essential features. There- fore, the detailed description of meiosis is based on observation of N. abnormis. The X and Y are positively heteropycnotic in early prophase and become isopycnotic by late diakinesis. The m-chromosomes are unpaired during the prophase and are negatively heteropycnotic at the first meta- phase. At the first metaphase, five auto- somal bivalents occupy the periphery of a spindle while the X and Y univalents and the m-chromosome lie in the center of the spindle (Fig. 22b). At the second metaphase, autosomes and the m-chro- mosome lie on the periphery of a hollow spindle while the XY pseudopair occupies the center of the spindle (Fig. 22c). 23. Nysius tenellus Barber. — The chro- mosome complement of Nysius tenellus is different from those of other species of the genus. The diploid chromosome num- ber of this species is 22 instead of 14. The spermatogonial metaphase consists of nine pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 23a). Four of the nine pairs of autosomes are larger than the others. There is no extremely large autosome pair, which occurs in all other species of the genus so far observed (see Table 3 and Fig. 22a). The X chromo- some is not easily distinguished from the autosomes, but may be intermediate be- tween large- and small-sized autosomes as shown by inspection of size relationship at the second metaphase (Figs. 23c, 131f). The Y chromosome is about one-third of the X in size. The m-chromosomes are a little smaller than the Y and are the smallest component in the set. The meiot- ic sequence of the species (Fig. 23b, c) is essentially the same as in other Nysius. 24. Rhypodes clavicornis (Fabricius) and R. myersi Usinger. — Rhypodes clavi- cornis and R. myersi are the same in their chromosome cytology. The spermatogonial metaphase contains five pairs of autosomes, a pair of m-chromosomes, and an XY sex Table 3. Relative size differences of chromosome complements in the genus Nysius (Orsil- linae) (EL, extra large; L, large; M, medium-sized; S, small). No. autosome pairs Species N. abnormis Usinger N. angustatus Uhler N. beardsleyi Ashlock V. caledoniae Distant N. coenosulus Stal N. communis Usinger N. ericae (Shilling) (= N. natalensis Evans) N. jullawayi Usinger N. huttoni B. -White N. lichenicola Kirkaldy N. longicollis Blackburn N. nemorivagus B. -White N. niger Baker N. raphanus Howard N. scutellatus Dallas N. stali Evans N. tenellus Barber N. usitatus Ashlock N. vinitor Bergroth N. sp. (?mixtus) EL M Sex chromosomes ~~ X Y 1/2Y 2/3Y 1/2Y 2/3Y 2/3Y 1/2Y 2/3Y Y Y Y 1/2Y Y Y 2/3Y Y Y 2/3Y 2/3Y Y Y S 1/3X M>X 1/3X S 1/2X S S M S S S S S M M S M S 1/3X 1/3X 1/4X 1/2X 1/3X 1/4X 1/3X 1/2X 1/3X 1/4X 1/3X 1/3X 1/2X M>X 1/3X S 1/3X S 1/3X S 1/3X 734 The University of Kansas Science Bulletin pair (Fig. 24a). One of the five pairs of autosomes is extremely large. The X chro- mosome is a little smaller than the four pairs of small autosomes and is about four times as large as the Y. The m-chromo- somes are slightly larger than the Y. The course of meiosis in these species (Fig. 24b, c) is the same as in Nysitts spe- cies. The m-chromosome is negatively het- eropycnotic in metaphase II. Orsillini. 25. Hudsona anceps (B.-White). — The diploid chromosome complement of Hud- sona anceps consists of five pairs of auto- somes, an m-chromosome pair, and an XY sex chromosome pair (Fig. 25a). One of the five pairs of autosomes is extremely large. The X chromosome is a little small- er than the small-sized autosomes and about four times as large as the Y. The m-chromosome is almost equal in size to the Y. The meiotic sequence of the spe- cies (Fig. 25b, c) is the same as in Nysius species. 26. Ortholomus arphnoides Baker and O. scolopax (Say). — Ortholomus arph- noides and 0. scolopax are the same in their chromosome cytology. The diploid chromosome complement consists of six pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 26a). In the spermatogonial metaphase, there are one extremely large pair, four medium-sized pairs, and one small pair of autosomes. The X chromosome belongs to the me- dium-sized group of autosomes. In O. arphnoides, the Y chromosome is about half the size of the X and slightly larger than the m-chromosome. In O. scolopax, the Y is one-third the size of the X and the same size as the m-chromosome. The meiotic sequence of these species (Fig. 26b, c) is the same as in Hudsona anceps and Nysius species described previously. 27. Ortholomus nevadensis Baker and 0. usingeri Ashloc\.— Chromosome cytol- ogy of Ortholomus nevadensis and O. usingeri is the same in essential features. The male diploid chromosome comple- ments consist of five pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 27a). In the spermatogonial metaphase of 0. nevadensis, two pairs of autosomes are larger than the other three pairs. One of these large pairs is ex- tremely large. The X chromosome is a little smaller than the small-sized auto- somes and about three times as large as the Y. The m-chromosomes are equal in size to the Y. In O. usingeri, size rela- tionships in the spermatogonial set are almost the same as in O. nevadensis. How- ever, the m-chromosomes are slightly smaller than the Y. The course of meiosis in these species (Fig. 27b, c) is as in Hudsona anceps and Nysius species. Isch n orhynchinae Three genera and seven species of the subfamily Ischnorhynchinae are now known cytologically. All the species show 14 (12 + XY) in their chromosome com- plements, including a pair of the m-chro- mosomes. Scudder (1962) suggested a possible relationship between Ischnorhyn- chinae and the Orsillinae from the evi- dence of the dorsal position of the abdom- inal spiracles, the structure of the oviposi- tor, and the chromosome number. The chromosome numbers in the Ischnorhyn- chinae are the same as in many Orsillinae, but in Ischnorhynchinae there is no ex- tremely large autosome pair, which is a characteristic of the Orsillinae. Also, the behavior of the X, Y, and the m-chromo- some during meiosis is quite different, particularly at the first metaphase, from that in the Orsillinae. Therefore, so far as chromosome cytology is concerned, the Ischnorhynchinae seem not to be closely related to the Orsillinae. In the Ischno- rhynchinae, the m-chromosome always takes a central position at metaphase I, but Cytotaxonomy of Lygaeidae 735 -P.-tb 25 Hudsona anceps •^'j |l; in T^~ a t | b f * I c ••• •• i • 1 Orsillinae ORSILLINI *b Ortholomus arphnoides ##a |!fib f '; • 2/ Ortholomus nevadensis SI Ischnorhynchinae • f b . <- 28 Caprhiobia pallipes t I . b • 0.%% a t I b * J 29 Kleidocerys franciscanus *•.«• till i m to •£ V ii * JU Pylorgus colon Fig. 25-30. Chromosomes of named species of Orsillinae and Ischnorhynchinae: a, spermatogonia! metaphase; b, first metaphase; c, second metaphase. {Exception Fig. 30: d, second anaphase.) Scale = 10 ^m. 736 The University of Kansas Science Bulletin the X and Y are peripheral in Caprhiobia and Kleidocerys, and the X is peripheral and the Y is central in Pylorgus. At metaphase II, the XY pseudopair and the m are central in both Caprhiobia and Pylorgus, while the XY pseudopair is central and the m-chromosome is periph- eral in Kleidocerys. 28. Caprhiobia pallipes Scudder and C. sp. (#116). — These two Caprhiobia species are the same in essential features of their chromosome systems. The sper- matogonial metaphase in both consists of five pairs of autosomes, an m-chromosome pair, and the X and Y sex chromosomes (Fig. 28a). In both species, one of the five pairs of autosomes is larger than the others. The X chromosome is similar in size to the four medium-sized pairs of autosomes, and is not easily distinguished from the autosomes. The Y is about two- thirds the size of the X and is more than twice as large as the m-chromosome. The course of meiosis in these species is a little different from others described. At the first metaphase, five autosomal tetrads and the X and Y dyads are usu- ally located on the periphery of a spindle and form a ring with the unpaired m- chromosomes in the center (Fig. 28b). The peripheral position of the sex chro- mosomes at the first metaphase is unusual in lygaeids. However, the second division of these species is quite orthodox. The X and Y pseudopair and the m-chromosome lie in the center of a ring of autosomes (Fig. 28c). 29. Kleidocerys jranciscanus (Stal), K. modestus Barber, and K. obovatus (Van Duzee). — The chromosome cytology of these three species of Kleidocerys is the same as in Caprhiobia pallipes in essential features. The diploid chromosome com- plement consists of five pairs of autosomes, an m-chromosome pair, and an XY pair (Fig. 29a). In these three species one of the five pairs of autosomes is smaller than the others. The X chromosome resembles the medium-sized group of autosomes and is not easily distinguished from the autosomes. In both K. jranciscanus and K. modestus, the Y chromosome is about one-third the size of the X and twice as large as the m-chromosome. In K. obo- vatus, the Y is half as large as the X and twice as large as the m-chromosome. The meiotic sequence of these species at metaphase I (Fig. 29b) is the same as in Caprhiobia pallipes. As the second metaphase is formed, the autosomes and the m-chromosome occupy the periphery of a spindle while the XY pseudopair lies in the center of the spindle (Fig. 29c). The peripheral position of the m-chromo- some at second metaphase is unlike that of the m in Caprhiobia pallipes. 30. Pylorgus colon (Thunberg). — The spermatogonial metaphase of Pylorgus colon consists of five pairs of autosomes, a pair of the m-chromosomes, and an XY sex pair (Fig. 30a). One of the five pairs of autosomes is larger than the others. The X chromosome is like the me- dium-group of autosomes and is not easily distinguished. The Y chromosome is about one-quarter the size of the X and about equal in size to the m-chromosome. The meiotic sequence of the species is similar to that in Kleidocerys jranciscanus, but not exactly the same. At metaphase I, five autosomal bivalents and the X chro- mosome lie on the periphery of a spindle, but usually the Y chromosome lies in the center of the spindle. The m-chromosome always takes a central position in the spindle (Fig. 30b). At metaphase II, the autosomes orient on the periphery while the XY pseudopair and the m-chromosome occupy the center of the spindle (Fig. 30c). As is usual in lygaeids, the m-chromosome is negatively heteropycnotic even at ana- phase II (Fig. 30d). Cytotaxonomy of Lygakidae 737 Cyminae The subfamily Cyminae as a group has the highest chromosome numbers in the Lygaeidae. In the Cymini, the two gen- era known cytologically, Cymodema and Cymus, are 28 (26 + XY) and 30 (28 + XY). Nesocymus, recently placed in the tribe Ontiscini (Hamid, 1975), is 22 (20 + XY). In the Ninini, three genera and four species have been investigated cyto- logically. The species of both Cymoninns and Ninomimus also show 22 (20 + XY). The genus Nintts has 16 (14 + XY), the lowest number so far known in the sub- family. The chromosome arrangement of the first and second metaphase in the Cyminae is variable. In the genera Cymus and Cymodema, the X, Y, and m take a cen- tral position, which is usual in lygaeids, at both first and second metaphase. How- ever, in Nesocymus of the Ontiscini and all the genera so far observed of Ninini, the X, Y, and m locate in the center of a spindle at the first metaphase, but the m takes a peripheral position at the sec- ond metaphase. The distribution pattern of chromo- some complements of the Cyminae is given in Figure 134. Cymini. 31. Cymus coriacipennis (Stal), C. lun- dus Stal, and C. sp. from Sierra, Califor- nia.— The diploid chromosome comple- ment of these Cymus species consists of 13 pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 31a). All the autosomes are similar in size. The X chromosome is not distinguishable from the autosomes. The Y chromosome is a little smaller than the autosomes and about four times as large as the m-chromosome. The essential features of meiosis in these three species are quite typical of the pattern of lygaeids described previously. The X and Y chromosomes are positively heteropyenotic in the early prophase. They are double structures composed of two sis- ter chromatids by the late diplotcne stage and are isopyenotic by late diakinesis. The autosomes reveal one chiasma on each, and the terminalization of chiasmata is completed by the prometaphase. The m- chromosomes are unpaired during the pro- phase and are negatively heteropyenotic at the first metaphase. They maintain this condition of negative heteropyenosis un- til the completion of meiosis. The 13 autosomal tetrads lie on the periphery of a hollow spindle while the X and Y dyads and the m-chromosome occupy the center of the spindle at both the first metaphase (Fig. 31b) and the second (Fig. 31c). The first metaphase arrangement of chromosomes in these spe- cies is not affected by the high chromo- some numbers, although there tends to be some disorder, which also accompanies high chromosome numbers in the other families of Heteroptera. The first division is equational for the sex chromosomes and reductional for the m-chromosome. The chromosome cytology of Cymus luridus was reported by Montgomery (1901£). He observed only the first meta- phase and simply stated that there were 15 chromosome entities. From his de- scription and illustrations, we can easily recognize the presence of the m-chromo- some, but he did not say anything about the sex-chromosome mechanism. From his observations, his specimens might be 12A + m + XY at metaphase I. If this assumption is true, the chromosome com- plements of his specimens and ours are different. 32. Cymus sp. (near waelbrocJ^i). — The diploid chromosome complement of this Cymus species is less by one pair of auto- somes than that of the previously described species. The spermatogonial metaphase consists of 12 pairs of autosomes, a pair of m-chromosomes, and the XY sex chro- 738 The University of Kansas Science Bulletin Cyminae • #§ a ft w D f w w»^ C CYMINI • •• •• b l«»»l, ran ■ •• * I ', • i II. .• I ••• 31 Cymus coriacipennis * ™ -^ a |*l *| b l*fl,c $& i r.» i i.; •» 32 Cymus sp. W near waelbroecki .*..* §»t«| b ,|llltc $& '••••»l ••mi JO Cymodema basicornis !0i ...... a ••••b ••!•'• On Nesocymus calvus • ONTISCINI k I » . c I * •■' #•• a b ••••Id 35 Cymoninus notabilis NININI *•• ■ .••:• »,V 00 Ninus insignis »; j . b t I ••?* a A • • b • ' m Chauliopinae 37 f • «' Chauliops bisontula Fig. 31-37. Chromosomes of named species of Cyminae and Chauliopinae: a, spermatogonial metaphase; b, first metaphase; c, second metaphase. (Exception Fig. 3 5: b and c, first metaphase; d, second metaphase.) Scale = 10 /im. Cytotaxonomy of Lygaeidak 739 mosomcs (Fig. 32a). One pair of auto- somes is larger than the others and is easily recognized. Again, the m-chromo- some is the smallest component in the set. The course of meiosis (Fig. 32b, c) in essential features is quite orthodox, and is like that in Cymus coriacipennis. 33. Cymodema basicornis Motschulsky. — The chromosome cytology of Cymode- ma basicornis is essentially similar to that of Cymus coriacipennis. The spermato- gonia! metaphase consists of 13 pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 33a). All the autosomes except the m pair are similar in size. The m pair is the smallest component, easily distinguished from the others. The X is not detectable, since it is the same size as the autosomes. However, the Y is smaller than the autosomes. The course of meiosis (Fig. 33b, c) is as in Cymus coriacipennis. Ontiscini. 34. Nesocymus caluus (B.-White). — The male diploid chromosome comple- ment of Nesocymus calvus consists of nine pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 34a). The nine pairs of autosomes are roughly simi- lar in size. The X and Y chromosomes are not distinguishable from the autosomes by size. However, from comparison with the second metaphase, the X may belong to the larger-sized group of autosomes and the Y to the medium-sized group. The m-chromosomes are the smallest compo- nents of the spermatogonial metaphase set and easily distinguished. The course of meiosis in the species (Fig. 34b, c) is as in Cymus luridus except that, at the second metaphase, the m- chromosome orients on the periphery of the spindle. The X and Y chromosomes are positively heteropycnotic in early pro- phase and become isopycnotic by late dia- kinesis. The m-chromosomes are unpaired during prophase and are negatively hetero- pycnotic at the first metaphase. Ninini. 35. Cymoninus notabilis (Distant) and C. turaensis (Paiva). — The chromosome cytology of Cymoninus notabilis and C. turaensis is the same in essential features. The spermatogonial metaphase consists of nine pairs of autosomes, a pair of m- chromosomes, and an XY sex pair (Fig. 35a). The nine pairs of autosomes are similar in size, and the X and Y are in- distinguishable from the autosomes. The smallest component is the m-chromosomes. The meiotic sequence (Fig. 35b-d) is as in Nesocymus calvus. The first meiotic division is reductional for the m-chromo- some and equational for the X and Y chromosomes. In C. notabilis, the Y chro- mosome is about one-third the size of the X and twice as large as the m-chromo- some. In C. turaensis, the X is about twice as large as the Y, which is three times as large as the m-chromosome. 36. Ninus insignis Stal. — The diploid chromosome complement of Ninus insig- nis consists of six pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 36a). In the spermatogonial meta- phase, the six pairs of autosomes are simi- lar in size. The X chromosome is not dis- tinguishable by size from the autosomes, but the Y is a little smaller than the auto- somes. The m-chromosomes are about one-third the size of the Y. The meiotic process (Fig. 36b, c) is as in Cymonius notabilis. Chauliopinae Only one genus and two species of the subfamily Chauliopinae have been studied cytologically. 37. Chauliops bisontula Banks and C. jallax Scott. — The essential features of chromosome cytology in Chauliops bison- tula and C. jallax are the same. The male 740 The University of Kansas Science Bulletin diploid chromosome complement consists of six pairs of autosomes, a pair of m- chromosomes, and an XY sex pair (Fig. 37a). In the spermatogonial metaphase, one pair of autosomes is very much larger than the others. Although the X chromo- some is not recognizable from the auto- somes by size, the Y is easily distinguished since it is smaller than all but the m-chro- mosomes. The m-chromosomes are the smallest component in the set. In the meiotic sequence, the X and Y chromosomes are positively heteropycnotic in early prophase. They are in nonhomol- ogous association and are double structures composed of two sister chromatids at the diffuse stage. Right after the diffuse stage, they separate from each other and they be- come isopycnotic by late diakinesis. The m-chromosomes are unpaired during the prophase and are negatively heteropycnotic at the first metaphase. Immediately after the diffuse stage, the tetrad nature of the six bivalents becomes evident. They are usually associated by one chiasma in each, and the terminalization of chiasmata is completed by the prometaphase. As the first metaphase is formed, six autosomal tetrads occupy the periphery of a spindle while the X and Y dyads and the m-chromosome lie in the center of the spindle (Fig. 37b). The first meiotic divi- sion is equational for the sex chromosomes and reductional for the m-chromosomes. At the second metaphase, the autosomes again orient on the periphery of a spindle and the XY pseudopair and the m-chro- mosome lie in the center of the spindle (Fig. 37c). Blissinae Ten genera and 37 species of the sub- family Blissinae have been cytologically studied. Of these, 23 species are 14 (12 + XY), including a pair of m-chromosomes and always one pair of extremely large autosomes. This status, which is also found in the Orsillinae, is characteristic of the subfamily. The genus Ischnodernus is a rather in- teresting group. The species with 16 chro- mosomes are distributed in temperate re- gions and the species with 14 chromosomes are found in the tropics. The species with 14 chromosomes always carry one pair of extremely large autosomes, but the species with 16 chromosomes do not. Therefore, the species with 16 chromosomes seem to be derived from the 14-chromosome spe- cies by fragmentation of the one large autosome pair. The distribution pattern of chromosome numbers may be correlated to the evolution and dispersal of the spe- cies in the genus Ischnodernus. Such a situation is also found in Macropes. Chro- mosome cytology in the species of Blissi- nae is quite orthodox. The X, Y, and m take a central position at both first and second metaphase. 38. Atrademus capeneri (Slater) and A. maritimus Slater and Wilcox. — The sper- matogonial metaphase of these two Atra- demus species consists of five pairs of auto- somes, an m-chromosome pair, and the X and Y sex chromosomes (Fig. 38a). One of the five pairs of autosomes is extremely large, much larger than the others, and easily distinguished. The relative sizes of the chromosome complements in these two species are given in Table 4. The course of meiosis in these two spe- cies is the same in every essential feature. As usual in lygaeids, at metaphase I the autosomal tetrads arrange themselves in the periphery of a spindle while the m- chromosomes and the X and Y dyads lie in the center of a ring formed by the auto- somes (Fig. 38b). As metaphase II is formed, the m-chromosomes and the XY pseudopair again are located in the center of a ring formed by five autosomal dyads (Fig. 38c). 39. Blissus arenarius Barber and other species in the genus Blissus.— The chromo- Cytotaxonomy of Lygaeidae a '£•• • % 1 38 Atrademus capeneri / i ; > 741 Blissinae ••'•• a | • b • t • t 1 it m t X 1/3X M 1/2X M 1/2X M>X 1/2X M>X 1/2X M 1/2X M 1/2X M 1/2X M>X 1/2X Cytotaxonomy of Lygaeidae 743 by late diakinesis. The m-chromosomes are unpaired during the prophase and are negatively heteropyenotic at the first meta- phase. The first meiotic division is reduc- tional for the m-chromosome and equa- tional for the sex chromosomes. In the second anaphase, the Xi and X2 segregate to one pole with one set of autosome halves and the Y goes to the other pole with the other set (Fig. 41d). 42. Cavelerins minor Slater and Miya- moto.— The chromosome complement of Cavelerius minor is somewhat different from that of C. illustris described pre- viously. The spermatogonial metaphase plate in C. minor consists of five pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 42a) instead of the X1X2Y multiple sex pair of C. illustris. One of the five autosome pairs is ex- tremely large. The X chromosome is slightly smaller than the autosomes and the Y is smaller than the X. The m-chro- mosomes, the smallest component in the diploid set, are readily distinguished from the rest of the chromosomes. The course of meiosis (Fig. 42b, c) is the same as in Bliss us arenarius. 43. Dimorphopterus blissoides (Baeren- sprung), D. annulatus (Slater), D. latus (Distant), D. oblongus (Stal), and S. syrtis Slater and Wilcox. — The male dip- loid chromosome complement of these five Dimorphopterus species consists of five pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 43a). One of the five autosome pairs is extremely large, much larger than the others. The X chromosome belongs to the medium- sized group of autosomes and is slightly larger than the smallest pair of autosomes. The Y chromosome is about half the size of the X and twice as large as the m-chro- mosome. The course of meiosis in these five species (Fig. 43b, c) is as in Blissus arenarius. 44. Geoblissus mef^ongensis Slater, Ash- lock, and Wilcox. — The male diploid chro- mosome complement of Geoblissus me- kpngensis consists of five pairs of auto- somes, a pair of m-chromosomes, and an XY sex pair (Fig. 44a). In the spermato- gonial metaphase, one of the five autosome pairs is extremely large, much larger than the others. The X chromosome is equal in size to the smaller-sized group of auto- somes. The Y chromosome is about one- third smaller than the X and is a little larger than the m-chromosome. The course of meiosis in the species (Fig. 44b, c) is as in Blissus arenarius. 45. Ischnodemus badius Van Duzee, /. brunnipennis (Germar), /. conicus Van Duzee, /. jalicus (Say), and /. slossoni Van Duzee. — The chromosome cytology of these five species of Ischnodemus is the same in essential features. The male dip- loid chromosome complement consists of six pairs of autosomes, a pair of m-chro- mosomes, and an XY sex pair (Fig. 45a). Relative size differences of chromosome complements in these species are given in Table 5. For example, in /. badius the six pairs of autosomes are similar in size. The X chromosome is smaller than the autosomes but larger than the Y. The m-chromosomes are about half the size of the Y and are the smallest components in the set. During meiosis, the X and Y chromo- somes are positively heteropyenotic in the early prophase and become isopyenotic by late diakinesis. They reveal nonhomolo- gous association at the diffuse stage and separate from one another at the diplotene stage. At the diplotene stage, they are double structures composed of two sister chromatids. The autosomes become evi- dent right after the diffuse stage and pass into a typical diakinesis. The m-chromo- somes are unpaired during the prophase; they are negatively heteropyenotic at the first metaphase and maintain this condi- tion through the completion of meiosis. 744 The University of Kansas Science Bulletin t t ft •JR»a ••:• * it • ••• L* < i Blissinae c 45 Ischnodemus badius -.#• a # • b t m 46 Ischnodemus noctulus ••• t » t ' •«" I ft • 47 Ischnodemus notandus^ •••• t » 4« Macchiademus diplopterus a $ b c tt 49 Macropes varipennis m" *•»%*** t,,u* 90 OU Macropes obnubilis #•••# • ft • • •* I 51 Micaredemus pusillus Gk W Fig. 45-51. Chromosomes of named species of Blissinae: a, spermatogonial metaphase; b, first metaphase; c, second metaphase. Scale = 10 fim. Cytotaxonomy of Lygaeidae 745 The course of meiosis in these species (Fig. 45b, c) is as in Bliss us arenarius. The chromosome cytology of /. falicus has been reported by Montgomery (1901/?, 1906). His findings are confirmed by our observations. 46. Ischnodemus noctulus Distant, /. nigrocephalus Slater, Ashlock, and Wil- cox, /. oblongus (Fabricius), /. brevicornis (Stal), and /. tibialis Stal. — These five species of Ischnodemus are the same in their chromosome cytology, but they are different from other Ischnodemus species described previously. The male diploid chromosome complement of these species consists of five pairs of autosomes, an m- chromosome pair, and an XY sex pair (Fig. 46a). One of the five pairs of auto- somes is extremely large, much larger than the others. Relative size differences of the chromosome complements in these species are given in Table 5. For exam- ple, in /. noctulus the X chromosome is the same size as the medium-sized auto- somes and the Y is smaller than the X. The m-chromosomes are the smallest com- ponents in the set and are about two-thirds the size of the Y. The course of meiosis of these species (Fig. 46b, c) is similar to that of Blissus arenarius. 47. Ischnodemus notandus Slater and Wilcox. — The chromosome cytology of Ischnodemus notandus is different from that of other species of the genus Ischno- demus so far studied cytologically. The male diploid chromosome complement consists of seven pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 47a). In the spermatogonial meta- phase, one of the seven pairs of autosomes is extremely large, much larger than the others. The remaining six pairs are simi- lar in size; however, two of them are slightly smaller than the other four pairs. The X chromosome belongs to the me- dium-sized group of autosomes and is not easily distinguished from them. The Y chromosome belongs to the smaller-sized group of autosomes and is slightly larger than the m-chromosomes, which are the smallest component in the set. The mei- otic sequence of the species (Fig. 47b, c) is similar to that in Blissus arenarius. 48. Macchiademus diplopterus (Dis- tant).— The essential features of chromo- some cytology in Macchiademus diplop- terus are the same as in Atrademus capen- eri. The spermatogonial metaphase con- sists of five pairs of autosomes, an m- chromosome pair, and the X and Y sex chromosomes (Fig. 48a). One of the five autosome pairs is extremely large, much larger than the others. The meiotic se- quence is as in Blissus arenarius (Fig. 48b, c). 49. Macropes varipennis (Walker), M. raja Distant, M. uniformis Distant, and M. sp. (PDA-41). — The chromosome cytology of these four species of Macropes is the same in essential features. The diploid chromosome complement in the male con- sists of five pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 49a). One of the five autosome pairs is extremely large, much larger than the others. Relative size differences of chromosome complements in these spe- cies are listed in Table 5. The course of meiosis in the species (Fig. 49b, c) is as in Blissus arenarius. 50. Macropes obnubilis (Distant). — The chromosome constitution of Macropes obnubilis is different from that in other Macropes species. The male diploid chro- mosome complement consists of six pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 50a). The six pairs of autosomes are similar in size. The X chromosome belongs to the medium-sized group of autosomes and the Y is half the size of the X. The m-chromosomes are one-third the size of the Y and are the smallest components in the set. The mei- 746 The University of Kansas Science Bulletin otic process of the species (Fig. 50b, c) is as in Bliss us arenarius. 51. Micaredemus piisillus (Dallas). — Micaredemus pusillus shows the same chromosome pattern as Macropes obnu- bilis. The spermatogonial metaphase con- sists of six pairs of autosomes, an m-chro- mosome pair, and an XY sex pair (Fig. 51a). One of the six autosomal pairs is larger than the others. The m pair is the smallest member of the set. The X chro- mosome belongs to the medium-sized group of autosomes, and so is not distin- guishable from the autosomes. However, the Y is half the size of the X and more than twice as large as the m. The course of meiosis (Fig. 51b, c) is quite orthodox and is as in Blissits arenarius. Henestarinae Only one species of the subfamily Henestarinae has been observed cytologi- cally. 52. Engistus viduus Slater. — The chro- mosome cytology of Engistus viduus is similar to that of Macropes varipennis in essential features. The diploid chromo- some complement of this species is five pairs of autosomes (one of these is more than twice as large as the rest), an m- chromosome pair, and the X and Y sex chromosomes (Fig. 52a). The m-chromo- somes are the smallest component in the set. The X belongs to the medium-sized groups of autosomes and the Y is smaller than the X. The meiotic sequence of the species is quite orthodox in every feature. The X and Y are heteropycnotic during the pro- phase and the m-chromosomes are un- paired during the prophase. At the first metaphase, as is usual, the five autosomal tetrads locate on the periphery of a spindle while the X and Y dyads and the m pair lie in the center of a ring formed by the autosomes (Fig. 52b). As the second meta- phase is formed, the XY pseudopair and the m pair again lie in the center of a ring formed by five autosomal dyads (Fig. 52c). Geocorinae Four genera and 13 species of the sub- family Geocorinae are now known cyto- logically. In the genus Geocoris, the chro- mosome number so far known is quite uniform and is 20 (18 + XY) in the diploid male. On the other hand, the genus Hypogeocoris shows two types (16 Table 5. Relative size differences of and Macropes (Blissinae) (EL, chromosome complements in the genera lschnodemus extra large; L, large; M, medium-sized; S, small). No. autosome pairs m Sex chromosomes Species EL lschnodemus baduis Van Duzee /. brevicornis (Stal) 1 /. brunnipennis (Germar) /. conicus Van Duzee I. jalicus (Say) /. nigrocephalus Slater, Ashlock, and Wilcox 1 I. noctulus Distant 1 1. notandus Slater 1 /. oblongus (Fabricius) 1 /. slossoni Van Duzee /. tibialis Stal 1 Macropes obnubilis (Distant) M. raja Distant 1 M. varipennis (Walker) 1 M. uniformis Distant 1 M. sp. (PDA-41) 1 M X Y 1/2Y M>X 2/3X 2/3Y M>X 1/2X 2/3Y M>X 2/3X 1/2Y M 2/3X Y M>X 1/2X 1/2Y M 2/3X 2/3Y M 2/3X 2/3Y M 2/3X 1/2Y M>X 2/3X 1/2Y M 1/2X 2/3Y M 1/2X 1/3Y M 1/2X 1/4Y M 2/3X 1/4Y M 2/3X 1/4Y M 2/3X 1/3Y M 1/2X 6 4 6 6 6 4 4 3 4 6 4 6 4 4 4 4 Cytotaxonomy of Lygaeidae 747 £ rlenestarinae •8?:" ( •:• <»:in •^ t • 3Z Engistus viduus W i3 n»^~.-;,. „«^;,-~i~.. ' Geocorinae W Geocoris atricolor * a lb c |t d 3^ Geocoris varius I b I • ».c ,'g* | I. ». . '. • ••• 30 Germalus sp. «•*• • • • • .'/•a •» • mh ••• c ypogeocons piceus $S i1!*. :iti::i,t Piocoris stellatus Fig. 52-57. Chromosomes of named species of Henestarinae and Geocorinae: a, spermatogonia! metaphase; b, first metaphase; c, second metaphase. (Exception Fig. 54: c, first anaphase; d, second metaphase.) Scale = 10 /am. 748 The University of Kansas Science Bulletin + XY and 14 + XY), as does the genus Piocoris (18 + XY and 14 + XY). At present it is difficult to judge the modal number of the subfamily. Compared to other species in the family, 20 (18 + XY) chromosomes is a fairly high chromosome number, found only in the Geocorinae and in the Drymini of the Rhyparochromi- nae. The chromosome behavior during mei- osis in the Geocorinae is somewhat un- orthodox. The first metaphase is quite usual, with the X, Y and m locating in the center of a hollow spindle. However, at metaphase II, the m-chromosome tends to arrange on the periphery with the auto- somes. Of course, the XY pseudopair lo- cates in the center. 53. Geocoris atricolor Montandon, G. bullatus (Say), G. pallens (Stal), G. sp. from Blythe, California, and G. sp. (PDA- 43). — These five species of Geocoris are the same in their chromosome cytology. The male diploid chromosome comple- ment of these species consists of eight pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 53a). Relative size differences of the chromosome com- plements in these species are listed in Table 6. In G. atricolor, for example, three pairs of autosomes are slightly larger than the others. The X chromosome belongs to the smaller-sized group of autosomes and is about twice as large as the Y. The m- chromosomes are one-third the size of theY. The X and Y chromosomes are posi- tively heteropycnotic in the early prophase of meiosis, and become isopycnotic by late diakinesis. They reveal nonhomologous association at the diffuse stage and sepa- rate from each other once at the diplotene stage. At the diplotene stage, they are revealed as double structures composed of two sister chromatids. Immediately af- ter the diffuse stage, the autosomes be- come evident and pass into a typical dia- kinesis. The m-chromosomes are unpaired during the prophase and are negatively heteropycnotic at metaphase I. At the first metaphase, eight autosomal tetrads occupy the periphery of a hollow spindle while the X and Y dyads and the m-chromosome lie in the center of the spindle (Fig. 53b). The first meiosis is reductional for the m-chromosome and equational for the sex chromosomes. At the second metaphase, the autosomes and the m-chromosome lie on the periphery of a spindle but the XY pseudopair occu- pies the center of the spindle (Fig. 53c). 54. Geocoris varius (Uhler). — Geocoris varins is different from the other Geocoris species described previously in chromo- some constitution. The diploid chromo- some complement in the male consists of six pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 54a). In the spermatogonial metaphase, six pairs of autosomes and the X chromosome are similar in size. The Y chromosome is half the size of the X and is larger than the m-chromosome. The course of meiosis of the species (Fig. 54b, d) is the same as in Geocoris atricolor. Figure 54c shows anaphase I. Table 6. Relative size differences of chromosome complements in the genus Geocoris (Geo- corinae) (EL, extra large; L, large; M, medium-sized; S, small). Species G. atricolor Montandon G. bullatus (Say) G. pallens Stal G. sp. (PDA-43) G. sp. (from Blythe, Calif.) No. autosome pairs m Sex chromosomes EL L M S X Y 3 2 2 4 3 5 6 6 •4 5 1/3Y 2/3Y 1/2Y 2/3Y 1/2Y S 1/2X M 1/3X S 1/2X S 1/3X S 1/2X Cytotaxonomy of Lygaeidae 749 55. Germalus sp. from New Caledonia. — The diploid chromosome complement in the male of the Germalus species con- sists of six pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 55a). One of the six autosome pairs is larger than the others. The X chromo- some is smaller than the small-sized auto- somes and is three times as large as the Y. The m-chromosomes are about half the size of the Y and are the smallest com- ponents in the spermatogonial metaphase plate. The meiotic sequence of the species (Fig. 55b, c) is as in Geocoris atricolor. 56. Hypogeocoris piceus (Say). — The male diploid chromosome complement of Hypogeocoris piceus consists of six pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 56a). In the sper- matogonial metaphase, one of the six auto- some pairs is larger than the others. The X chromosome is smaller than any auto- some and is twice as large as the Y. The m-chromosomes are half the size of the Y and are the smallest components in the set. The course of meiosis (Fig. 56b, c) is as in Geocoris atricolor. 57. Piocoris stellatus Montandon. — The chromosome cytology of Piocoris stellatus is similar to that of Geocoris atricolor, previously described. The diploid chro- mosome complement consists of eight pairs of autosomes, an m-chromosome pair, and the X and Y sex chromosomes (Fig. 57a). Two pairs of autosomes are slightly larger than the others but not conspicuously so. The X is the same size as the autosomes; the Y is smaller than the X and more than twice as large as the m-chromosome. The meiotic process of this species (Fig. 57b, c) is quite orthodox, as in Geocoris atricolor. Figure 57c shows the side view of metaphase II. Oxycareninae Three genera and five species in the subfamily Oxycareninae have been cyto- logically investigated. Essentially, all the species are the same in chromosome cytol- ogy, although three species of Oxycarenus have multiple sex chromosomes. A char- acteristic of the subfamily is lack of the m-chromosome. Menon (1955) reported the presence of m-chromosomes in O. hy- ahninpennis in some but not all of the cells within an individual. From his de- scription of meiosis and drawings, the m- chromosomes in O. hyalinipennis do not behave as they do in other lygaeids. Ap- parently, he did not observe in sufficient detail the behavior of the m-chromosomes during meiosis, and we are doubtful of the presence of the m-chromosome. What Menon thought were m-chromosomes might have been either parts of fractured chromosomes or supernumerary chromo- somes. The behavior of the X and Y during meiosis is usual. They are located in the center of a ring formed by the auto- somes at both metaphase I and metaphase II. 58. Crophius bohemani (Stal). — The spermatogonial metaphase in Crophius bo- hemani reveals seven pairs of autosomes and an XY sex pair (Fig. 58a). Three of the seven autosomal pairs are larger than the others. The X chromosome belongs to the smaller-sized group of autosomes and is not distinguishable. The Y chro- mosome is smaller than the X and is easily recognized by its size. In meiosis, the X and Y chromosomes are positively heteropycnotic in the early prophase and become isopycnotic by the late diakinesis. They are in nonhomolo- gous association at the diffuse stage and separate once in the diplotene stage. At the diplotene stage, they can be resolved as double structures. The autosomes be- come evident immediately after the dif- fuse stage and pass into typical diakinesis. They are usually associated by one chias- ma on each, and the terminalization of 750 The University of Kansas Science Bulletin JO Crophius bohemani w Vl Oxycareninae ..•.• a !..'-b t't c ;•, ,♦, a ••• | f • • • J3 Oxycarenus luctuosus a 60 Pachygronthinae PACHYGRONTHINI Oedancala dorsalis m 9 b c *$: | • ••.'•• .. ,.,d • f«tb Dl Pachygrontha bipunctata Ate a V.' D& Pachygrontha longiceps b •/•• a .••V •••• 00 Pachygrontha barberi t lit II «.'U a •Si1 b4 Uttaris pallidipennis •••• t • • t b • ». d d Fig. 58-64. Chromosomes of named species of Oxycareninae and Pachygronthinae: a, spermatogonial meta- phase; b, first metaphase; c, second metaphase; d, second anaphase. Scale = 10 /um. Cytotaxonomy of Lycaeidae 751 chiasmata is completed by the prometa- phase. The course of meiosis is usual. As the first metaphase is formed, seven auto- somal tetrads lie on the periphery of a spindle, but the X and Y dyads occupy the center of the spindle (Fig. 58b). The first meiosis is equational for the sex chromo- somes. At the second metaphase, the auto- somes again orient on the periphery of a spindle as the XY pseudopair lies in the center of the spindle (Fig. 58c). No m- chromosome is evident. 59. Oxycarenus luctuosus (Montrou- zier).— The male diploid chromosome complement of Oxycarenus luctuosus con- sists of seven pairs of autosomes and the X1X2Y multiple sex pair (Fig. 59a). Two of the seven autosome pairs are slightly larger than the others. The Xi chromo- some is equal in size to the small auto- somes and the X2 is about half the size of the Xi. The Y chromosome is inter- mediate in size between Xi and X2. The meiotic sequence of the species (Fig. 59b, c) is similar to that of Crophius bohemani. The Xi, X2, and Y chromo- somes are positively heteropycnotic in the early prophase and become isopycnotic by late diakinesis. In anaphase II, the Xi and X2 segregate to one pole with one set of autosomes and the Y goes to the other pole with the other set (Fig. 59d). As in Crophius, no m-chromosome is present. Pack ygro n th inae In the pachygronthine tribe Pachygron- thini, three genera and nine species are known cytologically. An interesting fea- ture of these members of the tribe, except for Uttaris, is the lack of the Y-chromo- some. The common chromosome number is 13 (12 + XO), including a pair of m- chromosomes. In Pachygrontha, three types of chromosome complements were found: 12 + XO, 16 + XO, and 22 + XO. This deviation from a common num- ber may have been caused either by frag- mentation or by chromatid autonomy, as is found in Thyanata or Banasa (Schrader and Hughes-Schrader, 1956, 1958). Study of the other species in the genus would be interesting from the point of view of chro- mosomal evolution and the holokinetic nature of the chromosomes. Chromosome cytology during meiosis in the tribe is quite orthodox. The X and m, and the Y if present, usually locate in the center of a hollow spindle at both first and sec- ond metaphase. In the tribe Teracriini, cytological data is now available for four genera and four species. All are 14 (12 + XY), including an m-pair. Fourteen chromosomes may be the modal number in the tribe. Chromo- some behavior during meiosis in the tribe is somewhat different from that in the Pachygronthini. Although the chromo- some arrangement at metaphase I is as in the Pachygronthini, at metaphase II, the m-chromosome tends to be located on the periphery with the autosomes instead of in the central position. In the subfamily Pachygronthinae, the essential chromosome number is 14 (12 + XY) and the Y chromosome was lost in Oedancala and Pachygrontha during the process of evolution. Pachygronthini. 60. Oedancala dorsalis (Say). — Oedan- cala dorsalis has been studied cytologically by Montgomery (1901a, 1906). Our find- ings confirm his observations. The male diploid chromosome complement of the species consists of five pairs of autosomes, an m-chromosome pair, and an X chromo- some (Fig. 60a). In the spermatogonia! metaphase, the five pairs of autosomes are similar in size. The X chromosome is smaller than any autosome, and the m- chromosomes are about one-third the size of the X and the smallest component in the set. 752 The University of Kansas Science Bulletin During meiosis, the X chromosome is positively heteropycnotic in the early pro- phase and becomes isopycnotic by late dia- kinesis. It can be resolved as a double structure composed of two sister chro- matids at the diffuse stage. The tetrad nature of the autosomes becomes evident right after the diffuse stage, and they pass into typical diakinesis. The m-chromo- somes are unpaired during the prophase and are negatively heteropycnotic. They maintain this condition until the comple- tion of meiosis. As metaphase I is formed, five auto- somal bivalents lie on the periphery of a spindle but the X dyad and m-chromo- some occupy the center of the spindle (Fig. 60b). The first meiosis is reductional for the m-chromosome and equational for the X chromosome. At metaphase II, again the X chromosome and the m-chromosome lie in the center of a ring formed by the autosomes (Fig. 60c). At anaphase II, the X chromosome moves to one pole (Fig. 60d). As a result of the second division, there are two types of spermatids: 5 + m + X and 5 + m. 61. Pachygrontha bipitnctata Stal, P. compacta Distant, P. lineata Germar, and P. nigrovittata Stal. — The chromosome cy- tology of these four species of Pachygron- tha is the same in essential features. The male diploid chromosome complement consists of five pairs of autosomes, an m- chromosome pair, and an X chromosome (Fig. 61a). In the spermatogonial meta- phase, the five pairs of autosomes are simi- lar in size. The course of meiosis (Fig. 61b, c) is the same as in Oedancala dor- salis. 62. Pachygrontha longiceps Stal. — Pach- ygrontha longiceps has two more pairs of autosomes than other Pachygrontha spe- cies previously described. The spermato- gonial metaphase of the species consists of seven pairs of autosomes, an m-chromo- some pair, and an X chromosome (Fig. 62a). The seven pairs of autosomes and the X chromosome are similar in size, while the m-chromosomes are the smallest components in the set and easily distin- guishable. The meiotic process of this species (Fig. 62b, c) is as in Oedancala dorsalis. There are two tvpes of anaphase II configurations (Fig.62d). 63. Pachygrontha barberi Slater. — The chromosome complement of Pachygrontha barberi is quite different from those of other species in the genus Pachygrontha. The spermatogonial metaphase of this spe- cies consists of ten pairs of autosomes, an m-chromosome pair, and a sole X chro- mosome (Fig. 63a). The ten pairs of auto- somes are similar in size, the X chromo- some is the largest component in the set, and m-chromosomes are the smallest. The course of meiosis (Fig. 63b, c) again is as in Oedancala dorsalis. The sole X goes to one pole with autosomes and the m-chromosome, leaving the other halves with no sex chromosome (Fig. 63d). 64. Uttaris pallidipennis (Stal). — The diploid chromosome complement of Ut- taris pallidipennis is five pairs of auto- somes, an m-chromosome pair, and the X and Y sex chromosomes (Fig. 64a). The chromosome system of the species is some- what different from that of other genera and species so far observed in the Pachy- gronthini. The genera Oedancala and Pachygrontha have shown the XO sex mechanism; Uttaris reveals the XY sys- tem, which is more common in the Ly- gaeidae. Nevertheless, the chromosome cytology of the species is as in the others, and the meiotic process (Figs. 64b, c) is quite orthodox. Teracriini. 65. Opistholeptus indicus Slater. — The male diploid chromosome complement of Opistholeptus indicus consists of five pairs Cytotaxonomy of Lygaeidae 753 {•% ••••:?.# b ft1 1 DJ Opistholeptus indicus t Pachygronthinae TERACRIINI % 00 Pachyphlegyas modigliani '$ li»*» Ml-I* 0/ Phlegyas abbreviates^ Mb • }&• • »» ft If1 c 68 Stenophyella macreta 9 Heterogastrinae • , • I 09 Dinomachellus maculatus t lb • | mm a • t D • • vw • i I • i • /U Dinomachus marshalli „ _ a lib || ^'♦ii • •?• * ' I 'hi Vi •• 71 Heterogaster behrensii Fie. 65-71. Chromosomes of named species of Pachygronthinae and Heterogastrinae: a, spermatogonial meta- phase; b, first metaphase; c, second metaphase. Scale = 10/im. 754 The University of Kansas Science Bulletin of autosomes, an m-chromosome pair, and XY sex pair (Fig. 65a). In the spermato- gonia! metaphase, one pair of autosomes is larger than the others and the remaining four pairs and the X chromosome are similar in size. The Y chromosome is half the size of the X and twice as large as the m-chromosomes. In meiosis, the X and Y chromosomes are positively heteropycnotic in early pro- phase and become isopycnotic by late dia- kinesis. They reveal nonhomologous as- sociation in the diffuse stage and in the diplotene stage, separate from each other. The five pairs of autosomes become evi- dent at the diplotene stage and pass into a typical diakinesis. The m-chromosomes are unpaired during the prophase and are negatively heteropycnotic at the first meta- phase. The course of meiosis (Fig. 65b, c) is as in Oedancala dorsahs except that at second metaphase, the m-chromosome lies on the periphery of the spindle with the autosomes (Fig. 65c). 66. Pachyphlegyas modigliani (Lethier- ry). — The chromosome complement of the male of Pachyphlegyas modigliani con- sists of five pairs of autosomes, a pair of m-chromosomes, and an XY pair (Fig. 66a). In the spermatogonial metaphase, five pairs of autosomes and the X chro- mosome are similar in size and the Y chromosome is smaller than the X. The m-chromosome is a third the size of the Y and the smallest component in the set. The course of the meiosis (Fig. 66b, c) is as in Opistholeptus indicus. 67. Phlegyas abbreviatus (Uhler). — Cytological study of Phlegyas abbreviatus had been done by Montgomery (\90\b, 1906). Our findings confirm his observa- tions. The spermatogonial metaphase con- sists of five pairs of autosomes, an m-chro- mosome pair, and an XY sex pair (Fig. 67a). All the autosomes and the X and Y sex chromosomes are similar in size; however, the Y is slightly smaller than the others. The m-chromosomes are the smallest components in the set. The mei- otic sequence (Fig. 67b, c) is as in Opis- tholeptus indicus. 68. Stenophyella macreta Horvath. — The male diploid chromosome comple- ment of Stenophyella macreta consists of five pairs of autosomes, an m-chromosome pair, and an XY pair (Fig. 68a). One of the five autosome pairs is larger than the others. The X chromosome is the same size as the smaller autosomes, and the Y is smaller than the X. The m-chromo- somes are the smallest components in the set and are a third the size of the Y. The course of meiosis is as in Opistho- leptus indicus except that in second meta- phase, the m-chromosome occupies the center of the spindle. (Fig. 68b, c). Heterogastrinae Three genera and six species of the subfamily Heterogastrinae have been in- vestigated cytologically. The chromosome number in Dinomachellus (three species) is 14 (12 + XY) and in Heterogaster (one species) and Masoas (two species) 16 (14 + XY). The modal number of the sub- family is uncertain. The behavior of chromosomes during meiosis in these species is quite orthodox. The X, Y and m take a central position at both first and second metaphase. 69. Dinomachellus maculatus Scudder and D. sp. (GGES-23). — The chromosome cytology of these two species of Dinoma- chellus is the same. The male diploid chromosome complement consists of five pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 69a). The five pairs of autosomes comprise one large pair, three medium-sized pairs, and one small pair. The X chromosome is the same size as the medium-sized autosomes and the Y is smaller than the small pair. The Cytotaxonomy of Lygaeidae 755 m-chromosomcs are the smallest compo- nents in the set. In meiosis, the X and Y chromosomes are positively heteropycnotic in the early prophase and form a nonhomologous as- sociation at the diffuse stage. They sepa- rate and are double structures composed of two sister chromatids at the diplotene stage. They become isopycnotic by late diakinesis. The autosomes become evi- dent after the diffuse stage and pass into a typical diakinesis. They are associated by one chiasma on each and the terminal- ization of chiasmata is completed by the prometaphase. The m-chromosomes are unpaired during the prophase and are negatively heteropycnotic at metaphase I. As the first metaphase is formed, five autosomal tetrads orient on the periphery of a spindle as the X and Y dyads and the m-chromosome lie in the center of the spindle (Fig. 69b). The first meiosis is equational for the sex chromosomes and reductional for the m-chromosome. At the second metaphase, the XY pseudopair and the m-chromosome lie in the center of a ring formed by the autosomes (Fig. 69c). 70. Dinomachus marshalli (Distant). — The essential features of chromosome cy- tology of Dinomachus marshalli are as in Dinomachellus maculatus. The spermato- gonial metaphase consists of five pairs of autosomes, an m-chromosome pair, and the X and Y sex chromosomes (Fig. 70a). The course of meiosis (Fig. 70b, c) is as in Dinomachellus maculatus. 71. Heterogaster behrensii (Uhler). — The male diploid chromosome comple- ment of Heterogaster behrensii consists of six pairs of autosomes, a pair of m-chro- mosomes, and an XY sex pair (Fig. 71a). The autosome pairs are composed of one large, four medium, and one small pair. The X chromosome belongs to the me- dium-sized group of autosomes and the Y is slightly smaller than the small-sized autosomes. The m-chromosomes are the smallest components in the set, and are half the size of the Y. The meiotic se- quence (Fig. 71b, c) is as in Dinoma- chellus maculatus, previously described. 72. Masoas transvaaliensis Distant and M. sp. (GGES-22). — The chromosome complement in these two species of Ma- soas is the same. The spermatogonial metaphase consists of six pairs of auto- somes, an m-chromosome pair, and an XY sex pair (Fig. 72a). Two of the six autosome pairs are smaller than the other four. The X chromosome is equal in size to the smaller autosomes, and the Y is smaller than the X. The m-chromosomes are the smallest components in the set, and are half the size of the Y. The meiotic sequence (Fig. 72b-d) is as in Dinomachel- lus maculatus. R h yparoch ro m in ae Cytologically as well as morphologi- cally, the Rhyparochrominae is heteroge- neous. It is the largest subfamily in the Lygaeidae and contains half the species in the family. Of these, 142 species in 67 genera have been worked out cytologically. Plinthisini. In the tribe Plinthisini, six species of the only genus are known cytologically. The chromosome number is 16 (14 + XY), including a pair of m-chromosomes. However, Pfaler-Collander (1941) report- ed 18 in the female diploid and 9 at first metaphase of oogenesis in Plinthisus pu- sillus. She did not observe any males. From her result, we may assume that the chromosome complement of P. pusillus is 17 (14 + XiXi.Y) in the male. The chromosome behavior in Plinthi- sus during meiosis is usual at metaphase I. However, the m-chromosome tends to take a peripheral position with the autosomes at metaphase II. The XY pseudopair lies in the center as usual. 73. Plinthisus compactus (Uhler), P. 756 The University of Kansas Science Bulletin IL Masoas transvaahensis •a? • ; t c tit •i '.jut Heterogastrinae d a • • • b 73 Plinthisus compactus Rhyparochrominae • PLINTHISINI A c • s • #?•• a #4 Cryphula nitens It'll I . 1 I LETHAEINI §m a I g b I I tl'ltf IJ Diniella nitida • t a tVi b 76 Diniella sp. PDA- 44 ••V -•••• »••• '••' 77 l I • amproceps sp. GGES-13 Fie. 72-77. Chromosomes of named species of Heterogastrinae and Rhyparochrominae: a, spermatogonia! meta- phase; b, first metaphase; c, second metaphase. (Exception Fig. 72: c and d, second metaphase.) Scale = 10 /im, Cytotaxonomy of Lycaeidae 757 longisetosus Barber, P. sp. (U-120), P. sp. (E-23), and P. sp. (C-27). — The chromo- some cytology of these five species of Plinthisus are the same. The male diploid chromosome complement of these species consists of six pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 73a). In the spermatogonial meta- phase, two of the six autosome pairs are slightly smaller than the others. Compara- tive size differences of chromosomes in these five species are given in Table 7. For example, in P. compactus, the X chromo- some belongs to the medium-sized group of autosomes and the Y is half the size of the X. The m-chromosomes are the smallest components in the set and are about one-third the size of the Y. In meiosis, the X and Y chromosomes are positively heteropycnotic in the early prophase and become isopycnotic by late diakinesis. They are in nonhomologous association at the diffuse stage and sepa- rate from each other in the diplotene stage. At the diplotene stage they can be resolved as double structures composed of two sister chromatids. The autosomes be- come evident right after the diffuse stage and pass into a typical diakinesis. They are associated by one chiasma on each, and the terminalization of chiasmata is completed by the prometaphase. The m- chromosomes are unpaired during the pro- phase and are negatively heteropycnotic at the first metaphase. They maintain this condition until the completion of meiosis. As the first metaphase is formed, six autosomal tetrads lie on the periphery of a hollow spindle, while the X and Y dyads and the m-chromosome occupy the center of the spindle (Fig. 73b). The first division is reductional for the m-chromo- some and equational for the sex chro- mosomes. As is usual in Heteroptera, the second meiosis follows directly from the first without any resting period. At the second metaphase, the XY pseudopair lies in the center of a ring formed by the autosomes and the m-chromosome (Fig. 73c). Leth aeini. Eight genera and 14 species of the tribe Lethaeini are now known cytologi- cally. The data so far available suggest that the modal number of the tribe is 13 (12 + XO). Deviation of chromosome number from 13 may be caused by frag- mentation where numbers increase and by fusion where they decrease. This tribe is characterized by a lack of the Y chromo- some, probably lost during chromosome evolution. The Y chromosome is also lacking in the genus Poeantius of the Rhyparochromini. Chromosome behavior during meiosis in the tribe is quite ortho- dox. The X and m take a central position at both metaphase I and metaphase II. 74. Cry p hula nitens Barber and C. trimaculata (Distant). — These two species of Cry p hula are the same in chromosome cytology. The spermatogonial metaphase consists of four pairs of autosomes, an m- chromosome pair, and the sole X chromo- some (Fig. 74a). One of four autosome pairs is larger than the others. The X Table 7. Relative size differences of chromosome complements in the genus Plinthisus (Rhy- parochrominae) (EL, extra large; L, large; M, medium-sized; S, small). Species P. compactus (Uhler) P. longisetosus Barber P. sp. (U-120) P. sp. (E-23) P. sp. (C-27) No. autosome paii 'S Sex chromosomes EL L M S m X Y 4 4 4 4 4 2 2 2 2 2 1/3Y 1/2Y 1/2Y 1/3Y 1/2Y M 1/2X M 1/3X M 1/2X M 1/2X M 1/2X 758 The University of Kansas Science Bulletin chromosome is smaller than any autosome and the m-chromosomes, the smallest com- ponents in the set, are easily distinguished. In meiosis, the X chromosome is posi- tively heteropycnotic in the early prophase, and is a double structure composed of two sister chromatids at the diffuse stage. By late diakinesis it has become isopycnotic. The autosomes become evident immedi- ately after the diffuse stage and pass into a typical diakinesis. The m-chromosomes are unpaired during the prophase and are negatively heteropycnotic at metaphase I. In metaphase I, four autosomal tetrads lie on the periphery, while the X dyad and the m-chromosomes occupy the center of a ring formed by the autosomes (Fig. 74b). Again at metaphase II, the X chromosome and the m-chromosome lie in the center of a ring formed by the autosomes (Fig. 74c). 75. Diniella nitida (Reuter), D. sp. (GGES-18), D. sp. (GGES-19), and D. sp. (GGES-20). — The chromosome cytol- ogy of these four species of Diniella are the same. The spermatogonial metaphase consists of five pairs of autosomes, an m- chromosome pair, and an X chromosome (Fig. 75a). In all four species, one pair of autosomes is larger than the others and the X chromosome is half the size of the small-sized autosomes. The m-chromo- somes are the smallest components in the set. The meiotic sequence of these spe- cies (Fig. 75b, c) is as in Crypluila nitens. 76. Diniella sp. (PDA-44).— The male diploid chromosome complement in this species of Diniella consists of six pairs of autosomes, one more than in other Dini- ella, an m-chromosome pair, and the sole X chromosome (Fig. 76a). The autosome pairs are similar in size and the X chro- mosome is smaller than the autosomes. The m-chromosomes are one-third the size of the X and are the smallest components in the spermatogonial metaphase set. The course of meiosis (Fig. 76b, c) is as in Cry ph ula nitens. In anaphase II, the X moves to one pole with one set of auto- some halves (Fig. 76d). 77. Lamproceps sp. (GGES-13). — The spermatogonial metaphase of this Lam- proceps species consists of five pairs of autosomes, an m-chromosomes pair, and an X chromosome (Fig. 77a). One pair of autosomes is larger than the others and the X chromosome is smaller than the autosomes. The m-chromosomes are the smallest components in the set. The course of meiosis (Fig. 77b, c) is as in Cry ph ula nitens. 78. Near Lamproceps sp. (GGES-21). — The male diploid chromosome comple- ment of this species near Lamproceps consists of five pairs of autosomes, a pair of m-chromosomes, and an X chromo- some (Fig. 78a). One of the five auto- some pairs is larger than the others and the X chromosome is about equal to the small-sized autosomes. The m-chromo- somes are the smallest component in the set. The course of meiosis (Fig. 78b, c) is as in Crypluila nitens. 79. Lethaeus barberi Slater.— The chro- mosome cytology of Lethaeus barberi is similar to that of Crypluila nitens in every essential feature. The spermatogonial met- aphase consists of four pairs of autosomes, an m-chromosome pair, and the X chro- mosome (Fig. 79a). One of the four auto- some pairs is quite a bit larger than the others. The X chromosome is similar in size to the medium-sized autosomes and cannot be distinguished from them. The m-chromosomes are the smallest compo- nent in the set. The course of meiosis (Fig. 79b, c) is as in Cry ph ula nitens. 80. Lethaeus sp. (GGES-11).— This spe- cies of Lethaeus has one more pair of autosomes than L. barberi, previously de- scribed. The spermatogonial metaphase consists of five pairs of autosomes, a pair of m-chromosomes, and the sole X chro- mosome (Fig. 80a). All the autosomes Cytotaxonomy of Lygaeidae 759 Rhyparochrominae # LETHAEINI 1ll /0 near Lamproceps sp GGES-21 • I I f.* I ^ • • J /" Lethaeus barberi ••• 0 0 * m- ~ lib |c Ad ••• II • • — 80 Lethaeus sp. - GGES-11 Ol Neolethaeus dallasi $& |l|:tlt *»•«« 82 Orbelli s sp. » » « « 83 Xestocoris nitens' Fig. 78-83. Chromosomes of named species of Rhyparochrominae: a, spermatogonia! metaphase; b, first meta- phase; c, second metaphase. {Exception Fig. 80: c and d, second metaphase.) Scale = 10 /im. 760 The University of Kansas Science Bulletin and the X chromosome are similar in size and the m-chromosomes are much smaller. The meiotic sequence (Fig. 80b-d) is as in Cry p hula nitens. 81. Neolethaeus dallasi (Scott). — The male diploid chromosome complement of Neolethaeus dallasi consists of five pairs of autosomes, a pair of m-chromosomes, and an X chromosome (Fig. 81a). In the spermatogonial metaphase, all the auto- somes and the X chromosome are similar in size. The m-chromosomes are the small- est component in the set. The course of meiosis (Fig. 81b, c) is as in Cryphula nitens. As at both meta- phases, five autosomal tetrads orient on the periphery of a spindle while the X and the m-chromosome lie in the center. 82. Orbellis sp. — The spermatogonial metaphase of this species of Orbellis con- sists of five pairs of autosomes, an m- chromosome pair, and the X chromosome (Fig. 82a). Of the five autosome pairs, one is large, one is medium-sized, and three are small. The X chromosome be- longs to the small-sized group of auto- somes. The m-chromosomes are the small- est components in the set. The chromo- some cytology and the meiotic sequence of the species (Fig. 82b, c) is as in Cryphula nitens, described previously. 83. Xestocoris nitens Van Duzee. — The spermatogonial metaphase of Xestocoris nitens consists of five pairs of autosomes, an m-chromosome pair, and the sole X chromosome (Fig. 83a). One of the auto- some pairs is larger than the others. The X chromosome is equal in size to the smaller autosomes, and the m-chromo- somes are the smallest components in the set. The meiotic sequence (Fig. 83b, c) is as in Cryphula nitens, with the X and the m-chromosome lying in the center of the spindle at both metaphases. Ozophorini. Only two genera and two species of the tribe Ozophorini have been investi- gated cytologically. One has a chromo- some number of 16 (14 + XY), and the other, Prosomoeus brunneus, which was observed by Muramoto (1973), 14 (12 + XY). We need more information to dis- cuss the characteristic chromosome cytol- ogy of the tribe. 84. Migdilybs jurcijer Hesse. — The dip- loid chromosome complement of Mig- dilybs jurcijer consists of six pairs of auto- somes, an m-chromosome pair, and the X and Y sex chromosomes (Fig. 84a). All six pairs of autosomes are similar in size. The X is the same size as the autosomes and the Y is slightly smaller than the X. The m-chromosomes are the smallest com- ponents in the set. The course of meiosis is quite orthodox. At metaphase I, six autosomal tetrads ar- range themselves on the periphery of a spindle while the X and Y dyads and the m-pair locate in the center of a ring formed by the autosomes (Fig. 84b). As is usual, the XY pseudopair and the m- chromosome lie in the center of a ring formed by the autosomes at second meta- phase (Fig. 84c). Antillocorini. Four genera and six species of the tribe Antillocorini have been studied cyto- logically. The modal number of the tribe appears to be 14 (12 -4- XY) including a pair of m-chromosomes. In Tropistethus holosericus, Pfaler-Collander (1941) could not clearly distinguish either the presence or absence of the m-chromosomes. How- ever, her Figure 19e suggests the presence of the m-chromosomes. Unfortunately, we did not have an opportunity to observe the species. In both Antillocoris and Cligenes, chro- mosome cytology during meiosis is a little unusual. At metaphase I, the X and Y locate in the center, while the m-chromo- some tends to locate on the periphery with Cytotaxonomy of Lygaeidae 761 • »• •• Rhyparochrominae OZOPHORINI %-' f I it 84 Migdilybs furcifer •*• a • • t b • .' ° Sii* ■i** i • t tit I ANTILLOCORINI § OJ Antillocoris minutus ##M a I b • c fit • • 00 Microcoris sexnotatus t a b t | •sis? »u« Hi « v ' 0/ Cligenes aethiops • ,»»•* •A1 hi Targarema stali TARGAREMINI Fig. 84-89. Chromosomes of named species of Rhyparochrominae: a, spermotogonial metaphase; b, first meta- phase; c, second metaphase. Scale = 10 /urn. 762 The University of Kansas Science Bulletin the autosomes. Metaphase II is quite or- thodox, with the XY pseudopair and the m arranging in the center. 85. Antillocoris minutus (Bergroth). — The male diploid chromosome comple- ment of Antillocoris minutus consists of five pairs of autosomes, a pair of m-chro- mosomes, and an XY sex pair (Fig. 85a). In the spermatogonia! metaphase, all the autosomes and the X chromosome are similar in size and the Y chromosome is smaller than the X. The m-chromosomes are the smallest components in the set. In meiosis, the X and Y chromosomes are positively heteropycnotic in the early prophase and become isopycnotic by late diakinesis. They are in nonhomologous association at the diffuse stage and main- tain this status until the early diplotene stage. In the late diplotene, they separate from each other and can be resolved as double structures. The tetrad nature of the autosomes becomes evident right after the diffuse stage, and they pass into a typical diakinesis. The m-chromosomes are unpaired during the prophase and are negatively heteropycnotic at the first meta- phase. As the first metaphase is formed, there are eight chromosome entities: five auto- somal tetrads, an m-chromosome tetrad, and the X and Y dyads (Fig. 85b). At the first metaphase, the autosomes and the m-chromosome are usually located on the periphery while the X and Y chromo- somes occupy the central position. The peripheral position of the m-chromosome at first metaphase is very unusual. At the second metaphase, the autosomes lie on the periphery of a spindle but the XY pseudopair and the m-chromosome oc- cupy the center of the spindle (Fig. 85c). 86. Microcoris sexnotatus (Bergroth). — The spermatogonial metaphase in Micro- coris sexnotatus consists of five pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 86a). All the autosomes and the X chromosome are similar in size and the Y chromosome is smaller than the X. The m-chromosomes are the small- est components in the set. The course of meiosis (Fig. 86b, c) is as in Antillocoris minutus. 87. Cligenes aethiops Distant and C. sp. (near ashanti). — The male diploid chro- mosome complement of these two species of Cligenes consists of five pairs of auto- somes, an m-chromosome pair, and the X and Y sex chromosomes (Fig. 87a). One of the five pairs of autosomes is larger than the others. The m-pair and the Y chromosome, being smaller, are easily distinguishable from the others, but the X is not recognizable in the spermato- gonial metaphase because it is the same size as the other autosomes. The meiotic sequence (Fig. 87b, c) is as in Antillocoris minutus in every essential feature. 88. Cligenes subcavicola Scudder. — Cli- genes subcavicola has one more pair of autosomes than C. aethiops, previously de- scribed. The spermatogonial metaphase consists of six pairs of autosomes, an m- chromosome pair, and the X and Y sex chromosomes (Fig. 88a). The six pairs of autosomes gradually decrease in size, and there are no clearly large autosomes as in C. aethiops. The course of meiosis in the species (Fig. 88b, c) is quite similar to that of Cligenes aethiops. At metaphase I, six pairs of autosomes lie on the periphery of a spindle while the m-chromosomes and the X and Y dyads are usually located in the center (Fig. 88b). The arrangement of the m-chromosome at the first meta- phase is different than in other antilloco- rines. Targaremini. Only one genus and species has been observed. Further cytological study of other species in this tribe is needed. 89. Targarema stall B.-White— The Cytotaxonomy of Lygaeidae 763 spermatogonia! metaphase of Targarema stall consists of seven pairs of autosomes and an XY sex pair (Fig. 88a). The auto- somes and X chromosome are similar in size, and the Y chromosome, the smallest component in the set, is easily distinguish- able. So far, no m-chromosome has been observed in this species. This status is very unusual in the Rhyparochrominae. In meiosis, the X and Y chromosomes are positively heteropycnotic and become isopycnotic by late diakinesis. They are in nonhomologous association and can be re- solved as double structures composed of two sister chromatids in the diffuse stage. In the diplotene stage they separate from each other. The autosomes, whose tetrad nature becomes evident immediately after the diffuse stage, are associated by one chiasma on each. The terminalization of chiasmata is completed by the prometa- phase. As the first metaphase is formed, usu- ally the seven autosomal tetrads and the X dyad lie on the periphery of a spindle while the Y chromosome occupies the cen- ter of the spindle (Fig. 89b). This ar- rangement at metaphase I for the X chro- mosome is very unusual. At the second metaphase, the XY pseudopair always lies in the center of a ring formed by auto- somes (Fig. 89c). Dry mini. Nine genera and 25 species of the tribe Drymini are now known cytologically. The data so far available indicate that the modal number of the tribe is 20 (18 + XY), including a pair of m-chromosomes. There are a few deviations from the mo- dal number. One species shows 18 (16 + XY) and three show 16 (14 + XY). These deviations from the modal number may have occurred by the fusion of auto- somes as in pentatomids (Schrader, 1947) and cimicids (Ueshima, 1966b). Thylo- chromus reveals 21 chromosomes due to the multiple sex chromosome mechanism. The distribution pattern of chromosome numbers in the tribe is given in Figure 135. Chromosome behavior during meiosis in the tribe Drymini is quite normal lor the Lygaeidae. At both first and second metaphases, the X, Y, and m take a cen- tral position in a hollow spindle. 90. Appolonius quadratus Scudder. — The spermatogonia! metaphase of Ap- polonius quadratus consists of seven pairs of autosomes, an m-chromosome pair, and the X .and Y sex chromosomes (Fig. 90a). Seven pairs of autosomes and the X are similar in size. The Y is about half as large as the other chromosomes. The m- pair is the smallest component in the set. In meiosis, the X and Y chromosomes are positively heteropycnotic and become isopycnotic by late diakinesis. They are in nonhomologous association at the diffuse stage and separate in the early diplotene stage. At the diplotene stage, they can be resolved as double structures. The auto- somes become evident right after the dif- fuse stage. The m-chromosomes are un- paired during the prophase and are nega- tively heteropycnotic at the metaphase. At the first metaphase, seven autosomal tetrads orient on the periphery of a spin- dle, while the X and Y dyads and the m-chromosomes lie in the center of the spindle (Fig. 90b). As is usual, the first division is reductional for autosomes and the m-chromosomes and equational for the sex chromosomes. At the second meta- phase, again the XY pseudopair and the m-chromosome lie in the center of a ring formed by autosomal dyads (Fig. 90c). 91. Dry m us units (Say). — The male diploid chromosome complement of Dry- mus units is eight pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 91a). All the autosomes and the X and Y chromosomes are similar in size; the m-chromosomes are much smaller. 764 The University of Kansas Science Bulletin • Rhyparochrommae A DRYMINI 90 Appolonius quadratus a | t g b c 91 „ • • 31 Drymus unus M a ff • • b • 9 9 •••* it •• 92 Eremocoris dimidiatus c a It ' .!». c • ; 93 Scolopostethus pacificus 94 Stilbocoris sp. PDA-34 C a A t ft b | SO Thylochromus nitidulus 7 • # Fig. 90-95. Chromosomes of named species of Rhyparochrominae: a, spermatogonial metaphase; b, first meta- phase; c, second metaphase. Scale = 10 yum. Cytotaxonomy of Lygaeidae 765 The course of meiosis (Fig. 91b, c) is as in Appolonius qaadratus, previously de- scribed. 92. Eremocoris dimidiatus Van Duzee, E. sp. near borealis (Dallas), E. inqiiiliniis Van Duzee, and E. opticus Van Duzee. — These four species of Eremocoris are the same in their chromosome cytology. The spermatogonia! metaphase consists of eight pairs of autosomes, an m-chromo- some pair, and an XY sex pair (Fig. 92a). All except the m-chromosomes gradually decrease in size from large to small. The m-chromosomes are the smallest compo- nents in the set and are easily distin- guished from other chromosomes. The meiotic sequence of these species (Fig. 92b, c) is as in Appolonius quadratus. 93. Scolopostethus pacificus Barber and S. thomsoni Reuter. — The chromosome cy- tology of these two species of Scoloposte- thus is the same. The spermatogonial metaphase consists of eight pairs of auto- somes, an m-chromosome pair, and an XY sex pair (Fig. 93a). In both species, two of the eight autosome pairs are slightly smaller than the others. The X chromo- some belongs to the medium-sized group of autosomes and the Y is smaller than the X. The m-chromosomes are the small- est components in the set. The course of meiosis (Fig. 93b, c) is as in Appolonius quadratus. 94. Stilbocoris sp. (PDA-34), S. sp. (GGES-14), S. sp. (GGES-15), and S. sp. (GGES-16). — These four species of Stil- bocoris are the same in their chromosome cytology in every essential feature. The spermatogonial metaphase consists of eight pairs of autosomes, an m-chromosome pair, and an XY pair (Fig. 94a). All except the m-chromosomes are similar in size. The m-chromosomes are the smallest com- ponents in the set. The meiotic process (Fig. 94b, c) is as in Appolonius quad- ratus. 95. Thylochromus nitidulus Barber. — The male diploid chromosome comple- ment of Thylochromus nitidulus consists of eight pairs of autosomes, an m-chromo- some pair, and the X1X2Y multiple sex pair (Fig. 95a). All except the m-chromo- somes gradually decrease in size from large to small. The m-chromosomes are smaller than any other chromosomes in the spermatogonial metaphase plate. The course of meiosis (Fig. 95b, c) is similar to that of Appolonius quadratus. The Xi, X2, and Y sex chromosomes are positively heteropycnotic in the early pro- phase and become isopycnotic by late dia- kinesis. As the result of the second divi- sion, there are two types of spermatids: 8 + m + X1X2 and 8 + m + Y. Stygnocorini. Two genera and five species of the tribe Stygnocorini have been studied. In Stygnocoris, three species have 16 (14 -f- XY), but S. rusticus reveals 18 (16 + XY) (see Fig. 96). This increased chromosome number may have been brought about either by fragmentation or by duplication of one pair of autosomes during chromo- some evolution. Chromosome cytology during meiosis in the tribe is quite ortho- dox. 96. Stygnocoris rusticus (Fallen). — The chromosome cytology of Stygnocoris rusti- cus has been studied by Pfaler-Collander (1941). Our findings confirm her observa- tions. The spermatogonial metaphase con- sists of seven pairs of autosomes, an m- chromosome pair, and an XY sex pair (Fig. 96a). All except the m-chromosomes are similar in size. The m-chromosomes are much smaller than the others and are easily distinguished. The course of meiosis is as in Drymus unus. At metaphase I, seven autosomal bivalents lie on the periphery of a hollow spindle while the X and Y univalents and the m-chromosomes orient in the center of the spindle (Fig. 96b). Again at meta- 766 The University of Kansas Science Bulletin fm m Rhyparochrominae W f • 9 STYGNOCORINI Iff • • • i * y.A • • t • t • ; 30 Stygnocori ygnocons rusticus |l ♦.'.•A a •|,|ib * • • V.V •»•§• • •»• 97 Clerada apicicornis # • % a I .) m « f #;J; tut » • I 98 Afrovertanus elongatus 99 Carpilis consimilis II* | t • _ h *» ## a • A b . • • c , •• • •• 1 UU Cnemodus albimaculus I • • b - » r c .'v *** a • • i 9* ' t 101 Exptochiomera dissimilis lib . «t CLERADINI MYODOCHINI •«& ■•is. • i lU* Heraeus pacificus Fig. 96-102. Chromosomes of named species of Rhyparochrominae: a, spermatogonia! metaphase; b, first meta- phase; c, second metaphase. Scale = 10 /mi. Cytotaxonomy of Lygaeidae 767 phase II, the XY pseudopair and the m- chromosome lie in the center of a ring formed by the autosomes (Fig. 96c). Cleradini. Only one genus and one species of the tribe Cleradini is known. This species, Clerada apicicornis, shows the highest chromosome number, 24 (22 + XY), so far observed in the Rhyparochrominae. The chromosome cytology of the spe- cies is usual at first division, but the m- chromosome tends to arrange on the pe- riphery at the second metaphase. 97. Clerada apicicornis Signoret. — The spermatogonia! metaphase of Clerada api- cicornis consists of ten pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 97a), the highest chromosome number in the Rhyparochrominae. The chromosomes gradually decrease in size from large to small. The m-chromosomes, the smallest components in the set, are readily recognized, but the X and Y chro- mosomes are not distinguishable. The course of meiosis (Fig. 97b, c) is essentially as in Drymus units except that the m-chromosome lies on the periphery of a hollow spindle in second metaphase. Myodochini. Sixteen genera and 43 species have been investigated. Of these, the great majority show 16 (14 + XY) chromosomes, but some show 14 (12 4* XY). In the genus Pachybrachius, four of the 18 species have 14 (12 + XY) chromosomes, and the re- maining 14 species have 16 (14 + XY). Two chromosomes may have fused to form one in these four species during their chromosome evolution. In Pachybrachius lateralis, two chromo- some types are found in Japan. The speci- mens which show 16 (14 -f- XY) are from Kyushu, while Takenouchi and Mura- moto (1967) reported 14 (12 + XY) chro- mosomes in specimens from Hokkaido. Further study is needed taxonomically as well as cytologically on the species. In the genus Paromius, four species show 14 (12 + XY) chromosomes, while one species, P. pallid us, reveals 12 (10 + XY) chromosomes. To date, cytological data suggest that the modal number of the Myodochini is 16 (14 + XY). If so, then 12 chromosomes in Paromius pallidas might be derived by spontaneous fusion. In P. pallid its, the largest pair of autosomes is much larger than the largest pair in other species of Paromius (see Figs. 106 and 107. This may indicate that spon- taneous fusion has taken place. Chromosome behavior during meiosis in the tribe is as usual at the first division. However, at second metaphase, the m- chromosome tends to locate on the periph- ery with the autosomes, while the XY pseudopair lies in the center as usual. The distribution pattern of chromo- some numbers in Myodochini is given in Figure 136. 98. Afrovertanus elongatus Scudder. — The male diploid chromosome comple- ment of Afrovertanus elongatus consists of five pairs of autosomes, a pair of m- chromosomes, and the X and Y sex chro- mosomes (Fig. 98a). In the spermato- gonial metaphase, all the autosomes and the X chromosome are similar in size. The Y chromosome is smaller than the X. The m-chromosomes are the smallest components in the set and are half the size of the Y. In meiosis, the X and Y chromosomes are positively heteropycnotic in the early prophase and become isopycnotic by late diakinesis. They are in nonhomologous association at the diffuse stage and are separate from each other in the diplotene stage, when they can be resolved as double structures. The autosomes become evident immediately after the diffuse stage and pass into a typical diakinesis. The m- chromosomes are unpaired during the pro- 768 The University of Kansas Science Bulletin phase and are negatively heteropycnotic at first metaphase. As the first metaphase is formed, five autosomal tetrads orient on the periphery of a spindle but the X and Y dyads and the m-chromosome lie in the center of the spindle (Fig. 98b). The first division is reductional for the m-chromosome and equational for the sex chromosomes. At the second metaphase, the autosomes and the m-chromosome lie on the periphery and the XY pseudopair occupies the cen- ter of the spindle (Fig. 98c). 99. Carpilis consimilis Barber. — The spermatogonial metaphase of Carpilis con- similis consists of six pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 99a). Two of the six pairs of autosomes are larger than the others. The X chromosome is equal to the small-sized group of autosomes and the Y is half the size of the X. The m-chromosomes are a third as large as the Y and the smallest component in the set. The course of meio- sis (Fig. 99b, c) is as in Afrovertanus elongatus. 100. Cnemodus albimaculus Berg and C. mavortius (Say). — The chromosome cy- tology of these two species of Cnemodus is the same. The spermatogonial meta- phase consists of six pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 100a). All the autosomes and the X and Y chromosomes are similar in size. The m-chromosome is the smallest component in the set. The meiotic se- quence (Fig. 100b, c) is as in Afrover- tanus elongatus. 101. Exptochiomera dissimilis Barber. — The male diploid chromosome comple- ment of Exptochiomera dissimilis consists of six pairs of autosomes, an m-chromo- some pair, and an XY sex pair (Fig. 101a). In the spermatogonial metaphase, the au- tosomes and the X chromosome gradually decrease in size from large to small. The Y chromosome is smaller than the X and about three times as large as the m-chro- mosome. The meiotic process (Fig. 101b, c) is as in Afrovertanus elongatus. 102. Heraeus pacifrcus Barber. — The spermatogonial metaphase of Heraeus pa- cificus consists of six pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 102a). All except the m-chro- mosomes gradually decrease in size from large to small. The m-chromosomes are smallest and are easily distinguishable from other chromosomes. The process of meiosis (Fig. 102b, c) is as in Afrover- tanus elongatus. 103. Ligyrocoris diffusus (Uhler), L. latimarginatus Barber, and L. litigiosus (Stal). — These three species of Ligyrocoris are the same in their chromosome cytol- ogy. The spermatogonial metaphase con- sists of six pairs of autosomes, an m-chro- mosome pair, and an XY sex pair (Fig. 103a). All except the m-chromosome grad- ually decrease in size from large to small. The m-chromosomes are the smallest com- ponents in the set. The course of meiosis (Fig. 103b, c) is as in Afrovertanus elon- gatus. 104. Pachybrachius albocinctus Barber and other species in the genus Pachybrach- ius.— The chromosome cytology of the fol- lowing observed species is the same: Pach- ybrachius albocintus Barber, P. bilobatus (Say), P. insularis (Barber), P. lateralis (Scott), P. limbatus (Stal), P. nesovinctus Ashlock, P. nietneri (Dohrn), P. vinctus (Say), P. sp. (PDA-46), P. sp. (GGES-8), P. sp. (GGES-9), P. sp. (GGES-10), and P. sp. (MLY-2). The spermatogonial metaphase consists of six pairs of autosomes, a pair of m- chromosomes, and an XY sex pair (Fig. 104a). In all the species, one of the six autosome pairs is larger than the others. Relative size differences of chromosome complements are given in Table 8. For instance, in P. albocinctus, the X chromo- some is slightly smaller than the medium- Cytotaxonomy of Lygaeidae 769 I ft I 103 Ligyrocoris diffusus ,'•••• a • ••: Rhyparochrominae C MYODOCHINI 104 Pachybrachius albocinctus ™ #S»a • • b 105 Pachybrachius pacificus : t • ♦ • i» b 106 Paromius apicatus $ % b *## t 107 Paromius pallidus " see text #•.:. a ! . • * « c 108 Pseudocnemodus canadensis Fig. 103-108. Chromosomes of named species of Rhyparochrominae: a, spermatogonial metaphase; b, first meta- phase; c, second metaphase. Scale = 10 /xm. 770 The University of Kansas Science Bulletin sized autosomes and is twice as large as the Y. The m-chromosomes are about one- third the size of the Y. The meiotic se- quence (Fig. 104b, c) is as in Afrover- tanus elongatus. 105. Pachybrachius pacificus (Stal), P. basalts (Dallas), P. capicola (Stal), and P. inconspicuus (Dallas). — The chromosome cytology of these four species of Pachy- brachius is the same, but they differ from other Pachybrachius species described pre- viously. The spermatogonial metaphase consists of five pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 105a). One of the five autosome pairs is larger than the others. The X chromosome is equal in size to the me- dium-sized autosomes and the Y is smaller than the X. The m-chromosomes are the smallest components in the set and are easily distinguished. Relative size differ- ences of chromosome complements in these four species are summarized in Table 8. The course of meiosis (Fig. 105b, c) is as in Afrovertanus elongatus. 106. Paromius apicatus (Stal), P. gra- cilis (Rambur), P. longulus (Dallas), and P. paraclypeatus Scudder. — These four spe- cies of Paromius are the same in their chromosome cytology. The male diploid chromosome complement consists of five pairs of autosomes, a pair of m-chromo- somes, and an XY sex pair (Fig. 106a). Two of the five autosome pairs are larger than the others. The X chromosome is equal in size to the small-sized autosomes and the Y is smaller than the X. The m- chromosomes are the smallest components in the set. The meiotic process (Fig. 106b, c) is as in Afrovertanus elongatus. 107. Paromius pallidus (Montrouzier). — Paromius pallidus has one less pair of autosomes than the other Paromius de- scribed previously. Malipatel (1978) has synonymized P. pallidus with P. gracilis, but they are treated separately here be- cause of the difference in chromosome complement. The spermatogonial meta- phase consists of four pairs of autosomes, a pair of m-chromosomes, and the X and Y sex chromosomes (Fig. 107a). Two pairs of autosomes are larger than the other two. The X chromosome is equal in size to the small-sized group of auto- somes and is larger than the Y. The m- chromosomes are the smallest components in the set. The course of meiosis (Fig. 107b, c) is as in Afrovertanus elongatus. Table 8. Relative size differences of chromosome complements in the genus Pachybrachius (Rhyparochrominae) (EL, extra large; L, large; M, medium-sized; S, small). Sex No. autosome pairs chromosomes Species P. albocinctus Barber ... P. basalts (Dallas) P. bilobatus (Say) P. capicola (Stal) P. inconspicuus (Dallas) P. insularis (Barber) P. lateralis (Scott) P. hmbatus (Stal) P. nesovinctus Ashlock . P. pacificus (Stal) P. nietneri (Dohrn) P. vinctus (Say) P. sp. (PDA-46) P. sp. (GGES-8) P. sp. (GGES-9) P. sp. (GGES-10) P. sp. (MLY-2) EL M X Y 1/3Y M>X 1/2X 1/4Y M>X 2/3X 2/3Y M 1/3X 1/3Y M>X 1/2X 1/2Y M 1/3X 1/2Y M 1/3X 1/3Y S 1/2X 1/3Y M 2/3X 1/2Y M>X 1/3X 1/3Y M 2/3X 1/4Y M 2/3X 2/3Y M 1/4X 1/4Y M 1/2X 1/2Y M>X 1/3X 1/2Y M 1/3X 1/2Y M 1/3X 1/3Y M 1/2X 5 4 4 4 4 5 4 5 5 4 5 5 5 5 5 5 5 Cytotaxonomy of Lygaeidak 771 108. Pseudocnemodus canadensis (Pro vancher). — The spermatogonia! metaphase of Pseudocnemodus canadensis consists of six pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 108a). All but the m-chromosome are similar in size. The X chromosome belongs to the me- dium-sized group of autosomes and is larger than the Y. The m-chromosomes are the smallest components in the set. The meiotic sequence (Fig. 108b, c) is as in Ajrovertanus elongatus. 109. Ptochiomera nodosa Say. — The male diploid chromosome complement consists of six pairs of autosomes, an m- chromosome pair, and an XY sex pair (Fig. 109a). In the spermatogonial meta- phase, all except the m-chromosomes are similar in size. The m-chromosomes are the smallest components in the set and are easily recognized. The meiotic process (Fig. 109b, c) is as in Ajrovertanus elon- gatus. 110. Remaudiereana nigriceps (Dallas) and R. sp. (MLY-3). — These two species of Remaudiereana are the same in their chromosome cytology. The spermatogo- nial metaphase consists of five pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 110a). One of the five autosome pairs is larger than the others. The X chromosome is equal in size to the medium-sized autosomes and is about twice as large as the Y. The m- chromosomes are much smaller than the Y and are the smallest components in the set. The course of meiosis (Fig. 110b, c) is as in Ajrovertanus elongatus. 111. Sphaerobius insignis (Uhler). — The male diploid chromosome comple- ment of Sphaerobius insignis consists of six pairs of autosomes, a pair of m-chro- mosomes, and an XY sex pair (Fig. Ilia). In the spermatogonial metaphase, all the autosomes are similar in size. The X chromosome is similar to the autosomes in size but larger than the Y. The m-chro- mosomes are the smallest components in the set. The course of meiosis (Fig. 111b, c) is as in Ajrovertanus elongatus. 112. Stigmatonotum capucinum (Stal). — The chromosome cytology of Stigmato- notum capucinum is as in Sphaerobius insignis, previously described. The sper- matogonial metaphase consists of six pairs of autosomes, an m-chromosome pair, and the X and Y sex pair (Fig. 112a). The meiotic sequence and the behavior of chro- mosomes during meiosis (Fig. 112b, c) is as in Sphaerobius insignis. 113. Togo hemipterus (Scott). — The spermatogonial metaphase of Togo hemip- terus consists of six pairs of autosomes, an m-chromosome pair, and the X and Y sex chromosomes (Fig. 113a). All except the m-chromosome are similar in size. The m-chromosomes are the smallest compo- nents in the set. The meiotic process (Fig. 113b, c) is as in Sphaerobius insignis. 114. Zeridonius costalis (Van Duzee). —The male diploid chromosome comple- ment in Zeridonius costalis consists of six pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 114a). In the spermatogonial metaphase, all the auto- somes and the X chromosome are similar in size. The Y chromosome is smaller than the X and much larger than the m- chromosomes. The meiotic sequence (Fig. 114b, c) is as in Sphaerobius insignis. Udeocorini. 115. Serranegra sp. — The chromosome cytology of this species of Serranegra is the same as in Paromius apicatus. The spermatogonial metaphase complement is five pairs of autosomes, an m-chromosome pair, and the X and Y sex chromosomes (Fig. 115a). One of the five pairs of auto- somes is larger than the others. The X belongs to the medium-sized group of autosomes and is not distinguishable from the autosomes. The m-chromosome is the smallest component in the set and is half 772 The University of Kansas Science Bulletin m , f « c Rhyparochrominae 109 Ptochiomera nodosa MYODOCHINI I b I . c • f I1Q Remaudiereana nigriceps a a ft Sphaerobius insignis M b t •: ■ c I • - I • • •• • f 112 Stigmatonotum capucinum in ** »• I I J Togo hemipterus 114 Zeridonius costalis Fig. 109-114. Chromosomes of named species of Rhyparochrominae: a, spermatogonia! metaphase; b, first meta- phase; c, second metaphase. Scale =: 10 fim. Cytotaxonomy of Lygaeidae 773 as large as the Y. The meiotic sequence (Fig. 115b, c) is quite orthodox. Rhyparochromini. Fourteen genera and 28 species in the tribe Rhyparochromini have been cytologi- cally investigated. This tribe is a rather heterogeneous group cytologically. Fifteen species show 14 (12 + XY) chromosomes and seven show 12 (10 + XY) chromo- somes. In addition, Graphoraglius novitus reveals 10 (8 + XY) chromosomes, the lowest number in the whole Lygaeidae. The three species of Poeantius so far stud- ied lack the Y chromosome, and Grapto- peltus japonicus carries multiple X chro- mosomes. Interestingly, Parshad (1957£) reported that the m-chromosomes of Lachnesthus singalensis were equational at the first di- vision and reductional at the second. If true, this is the only case of such behavior of the m-chromosomes in the whole fam- ily. However, he did not observe the detailed behavior of the m-chromosomes, and his drawings seem to show that the m-chromosomes are already double struc- tures and positively heteropycnotic at early diakinesis. According to our observations, the m-chromosomes are not positively het- eropycnotic during prophase, and they are negatively heteropycnotic at metaphase I and II. He does not mention negative heteropycnosis at either first or second metaphase. Moreover, he did not draw or describe the side view of anaphase I, which is the most critical stage to prove either equational or reductional separa- tion. For these reasons, we doubt that the m-chromosomes of L. singalensis are equa- tional at the first division. More detailed work must be done on the behavior of the m-chromosomes in this species. Chromosome behavior during meiosis in the tribe is more or less heterogeneous. Most genera and species show the usual pattern in spermatogenesis. However, in Peritrechus and Poeantius, the m lies in the center of a spindle with the sex chro- mosomes at first metaphase and tends to arrange on the periphery with the auto- somes at the second metaphase (see Figs. 124 and 126). 116. Anepsiodes nitidus Reuter. — The male diploid chromosome complement of Anepsiodes nitidus consists of five pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 116a). In the sper- matogonial metaphase, all the autosomes and the X chromosome are similar in size. The Y chromosome is smaller than the X and larger than the m-chromosomes. In meiosis, the X and Y chromosomes are positively heteropycnotic in the early prophase and become isopycnotic by late diakinesis. They are in nonhomologous association at the diffuse stage and are separate in the diplotene stage. At the diplotene stage, they are double structures composed of two sister chromatids. The autosomes become evident right after the diffuse stage and pass into a typical dia- kinesis. The m-chromosomes are unpaired during the prophase and are negatively heteropycnotic at metaphase I. As metaphase I is formed, five auto- somal tetrads locate on the periphery of a hollow spindle while the X and Y dyads and the m-chromosome orient in the cen- ter of the spindle (Fig. 116b). The first division is equational for the sex chromo- somes. The second meiosis follows direct- ly after the first without any resting stage. At metaphase II, the autosomal dyads lie on the periphery of a spindle as the XY pseudopair and the m-chromosome orient in the center of the spindle (Fig. 116c). 117. Aphanus sp. (PDA-33).— The sper- matogonial metaphase of this Aphanus species consists of five pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 117a). All except the m-chro- mosomes gradually decrease in size from large to small. The m-chromosomes are 774 The University of Kansas Science Bulletin Rhyparochrominae a ft ' A b * • c lit) Serranegra sp. UDEOCORINI lib Anepsiodes nitidus^ RHYPAROCHROMINI a t «b m | V;* •••»• V"« 17 Aphanus sp. PDA-33 • a lb 9 ••••I • 5 I 9 • 118 Dieuches sp. - PDA- 14 119 Dieuches basiceps ™W • ftp • > w t ft *• * a w d I • c {# • ••••• i : t t • » IZU Elasmolomus transversus Fig. 115-120. Chromosomes of named species of Rhyparochrominae: a, spermatogonial metaphase; b, first meta- phase; c, second metaphase. (Exception Fig. 119: c, first anaphase; d, second metaphase.) Scale = 10 yum. Cytotaxonomy of Lygaeidae 775 the smallest components in the set and are readily recognized. The course of meiosis (Fig. 117b, c) is as in Anepsiodes nitidus, previously described. 118. Dieuches sp. (PDA-14), and D. sp. (69-17). — The spermatogonial metaphase of these two Dieuches species consists of four pairs of autosomes, a pair of m-chro- mosomes, and an XY sex pair (Fig. 118a). One of the four autosome pairs is very much larger than the others. The m- chromosomes are the smallest components in the set and are easily distinguished from the rest. The meiotic sequence (Fig. 118b, c) is as in Anepsiodes nitidus. 119. Dieuches sp. (prob. patruelis). — This species of Dieuches has one more pair of autosomes than the other species of Dieuches described. There are five pairs of autosomes, an m-chromosome pair, and the X and Y sex chromosomes in the sper- matogonial metaphase (Fig. 119a). Al- though there is a large pair of autosomes in Dieuches sp. (PDA-14) and D. sp. (69-17), no large pair of autosomes is recognized in this species. The course of meiosis is as in the spe- cies previously described in essential fea- tures. At the first metaphase, there are five autosomal tetrads, an m tetrad, and the X and Y dyads (Fig. 119b). The m- chromosomes are reductional and the X and Y are equational at the first division (Fig. 119c). As is usual, there are five autosomal dyads, the m-dyad, and the XY pseudopair at the second metaphase (Fig. 119d). 120. Elasmolomus transversus (Signo- rett), and E. mendicus Stal. — These two species of Elasmolomus are the same in their chromosome cytology. The male dip- loid chromosome complement consists of five pairs of autosomes, a pair of m-chro- mosomes, and the X and Y sex chromo- somes (Fig. 120a). One of the five auto- some pairs is larger than the others, and the smallest pair is the m-chromosomes. The course of meiosis (Fig. 120b, c) is as in Anepsiodes nitidus. 121. Graphoraglius novitus (Distant). — Graphoraglius novitus has the lowest chro- mosome number in the Lygaeidae. The spermatogonial metaphase contains three pairs of autosomes, a pair of m-chromo- somes, and an XY sex pair (Fig. 121a). One of the three autosome pairs is very much larger than the others. The X chro- mosome belongs to the small-sized group of autosomes and the Y is smaller than the X. The m-chromosomes are the small- est components in the set. The course of meiosis (Fig. 121b, c) is quite orthodox and is the same as in Anepsiodes nitidus. 122. Metochus uniguttatus (Thunberg). — The chromosome cytology of Metochus uniguttatus had been investigated by Manna (1951). Our observations confirm his findings. The spermatogonial meta- phase of the species consists of four pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 122a). One of the autosome pairs is very much larger than the others. The m-chromosomes are the smallest components in the set. The meiotic process (Fig. 122b, c) is as in Anepsiodes nitidus. 123. Naudarensia manipurensis Distant. — The spermatogonial metaphase of Nau- darensia manipurensis consists of five pairs of autosomes, an m-chromosome pair, and an XY sex pair (Fig. 123a). All except the m-chromosomes gradually decrease in size from large to small. The m-chromo- somes are the smallest components in the set. The course of meiosis (Fig. 123b, c) is as in Anepsiodes nitidus. 124. Peritrechus tristis Van Duzee. — The male diploid chromosome comple- ment of Peritrechus tristis consists of five pairs of autosomes, a pair of m-chromo- somes, and an XY sex pair (Fig. 124a). All except the m-chromosomes are similar in size. The m-chromosomes, much small- 776 The University of Kansas Science Bulletin Rhyparochrominae RHYPAROCHROMINI 121 Graphoraglius novitus *•* a m. b A * \/J MpfnrVinc tin icrn4- + at-iic 122 Metochus uniguttatus ,23 • %% Itu Naudarensia manipurensis .«-a • b • c •Sv * ■•■ ■ % t m It4 Peritrechus tristis a _ f |b f c IZO Phorcinus albofasciatus <« !'••• •:•• «■# • • t • t IZo Poeantius festivus ^P Fig. 121-126. Chromosomes of named species of Rhyparochrominae: a, spermatogonial metaphase; b, first meta- phase; c, second metaphase. (Exception Fig. 126: d, second anaphase.) Scale = 10 /mi. Cytotaxonomy of Lygaeidae 777 cr than any other chromosomes, arc the smallest components in the set. The meiotic sequence (Fig. 124b) is similar to that of Anepsiodes nitidus ex- cept that as the second metaphase is formed, the autosomes and the m-chromo- some locate on the periphery of a spindle as the XY pseudopair lies in the center (Fig. 124c). This arrangement of the m- chromosome at the second metaphase is unlike that in most other species in the Rhyparochromini. 125. Phorcimts albofasciatus (Stal). — The chromosome cytology of Phorcimts albofasciatus is the same as in Naudaren- sia manipurensis. The spermatogonia! metaphase of the species consists of five pairs of autosomes, an m-chromosome pair, and the X and Y sex chromosomes (Fig. 125a). The five pairs of autosomes and the X are similar in size. The Y is much smaller than the X, but is more than twice as large as the m-chromosome. The course of meiosis (Fig. 125b, c) is quite orthodox. 126. Poeantius jestivus Distant, P. sp. (Thailand), and P. sp. (#128).— Chromo- some cytology of these three species of Poeantius is the same. The spermato- gonia! metaphase consists of five pairs of autosomes, a pair of m-chromosomes, and the sole X chromosome (Fig. 126a). All except the m-chromosome are similar in size. The m-chromosomes are much the smallest components in the set. Jande (1959a) reported the chromosome system of P. jestivus. His observation is the same as our findings. The course of meiosis is similar to that of Phorcimts albofasciatus. However, these Poeantius species have no Y chromosome. At metaphase I, five autosomal tetrads take a peripheral position while the X dyad and the m-chromosome usually lie in the center of the spindle (Fig. 126b). The first meiosis is reductional for the m-chromosomes and equational for the X chromosome. At metaphase II, the X chromosome locates in the center of a ring formed by the autosomes and the m-chro- mosome (Fig. 126c). This unusual ar- rangement of the m-chromosome is similar to that of Peritrechus tristis. At anaphase II, the X moves to one pole (Fig. 126d) and, as the result of the second division, there are two types of spermatids: 5 -f- m + X and 5 + m. Megalonotini. Two genera and three species have been studied by Pfaler-Collander (1941; see Table 10). Essentially, the chromo- some complements are the same, the dif- ferences being due to the number of X chromosomes. We have no new data on this tribe. Gonianotini. To date, seven genera and eight species have been investigated. This tribe contains three types of chromosome complements: 14 (12 + XY), 16 (14 + XY), and 18 (16 + XY). The modal number of chro- mosomes for the tribe is not yet clear. The chromosome cytology during meiosis is orthodox at first meiosis, but at second, the m-chromosome tends to locate on the periphery instead of in the usual central position. 127. Delochilocoris illutninatus (Dis- tant).— The spermatogonial metaphase of Delochilocoris illutninatus consists of six pairs of autosomes, a pair of m-chromo- somes, and an XY sex pair (Fig. 127a). One of the six autosome pairs is smaller than the others and is equal in size to the Y. The X chromosome may belong to the medium-sized group of autosomes and is not distinguishable from the autosomes. The m-chromosomes are the smallest com- ponents in the set. In meiosis, the X and Y chromosomes are positively heteropycnotic in the early prophase and become isopycnotic by late diakinesis. They are in nonhomologous 778 The University of Kansas Science Bulletin association at the diffuse stage and sepa- rate in the early diplotene stage. In the diplotene, they can be resolved as double structures. The tetrad nature of the auto- somes becomes evident right after the dif- fuse stage and they pass into a typical diakinesis. The m-chromosomes are un- paired during the prophase. As metaphase I is formed, six auto- somal tetrads orient on the periphery of a hollow spindle, with the X and Y dyads and the m-chromosomes in the center (Fig. 127b). The first meiosis is equa- tional for the sex chromosomes and reduc- tional for the m-chromosomes. The second meiosis follows directly after the first with- out any resting stage. At metaphase II, the XY pseudopair orients in the center a ft f 127 Delochi locoris i 1 lumina tus of a spindle formed by the autosomes and the m-chromosome (Fig. 127c). 128. Emblethis vicarius Horvath. — The spermatogonial metaphase of Emblethis vicarius consists of five pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 128a). One pair of autosomes is very much larger than the others, three pairs are medium-sized, and one is small. The X is the same size as the medium- sized autosomes, and the Y is similar in size to the small autosomes. The m-chro- mosomes are the smallest components in the set. The meiotic sequence (Fig. 128b, c) is similar to that of Delochilocoris il- luminatits in essential features. 129. Malezonotus sodalicius (Uhler). — The male diploid chromosome comple- ^ Rhyparochrominae j • • c GONIANOTINT a 128 • tb Emblethis vicarius • : ) • * 0% a in I/O Malezononus sodalicius ••V a b 130 Meschia sp. PDA-6 i : • t t Subfamily ? Fie. 127-130. Chromosomes of named species of Rhyparochrominae and of Meschia, incertae sedis: a, sperma- togonial metaphase; b, first metaphase; c, second metaphase. Scale = 10 fim. Cytotaxonomy of Lygaeidae 779 merit of Malezonotus sodalicius consists of six pairs of autosomes, a pair of m-chro- mosomes, and an XY sex pair (Fig. 129a). All the autosomes gradually decrease in size from large to small. The m-chromo- somes are the smallest components in the set. The course of meiosis (Fig. 129b, c) is as in Delochilocoris illuminatus. Incertae Sedis 130. Meschia sp. (PDA-6).— The sper- matogonial metaphase of this species of Meschia consists of six pairs of autosomes, a pair of m-chromosomes, and an XY sex pair (Fig. 130a). One of the six autosome pairs is larger than the others. The Y chromosome is smaller than autosomes and is larger than the m-chromosomes. The m-chromosomes are the smallest com- ponents in the set. In meiosis, the X and Y chromosomes are positively heteropyenotic in early pro- phase and become isopyenotic by late dia- kinesis. They are in nonhomologous as- sociation at the diffuse stage and are separate at the diplotene stage. At the diplotene stage they can be resolved as double structures. The autosomes become evident right after the diffuse stage and pass into a typical diakinesis. The m- chromosomes are unpaired during the pro- phase and are negatively heteropyenotic. As the first metaphase is formed, six autosomal bivalents lie on the periphery of a hollow spindle while the X and Y uni- valents and the m-chromosome orient in the center of the spindle (Fig. 130b). At the second metaphase, the XY pseudopair lies in the center of a ring formed by the autosomes and the m-chromosomes (Fig. 130c). Systematic and Cytological Discussion Slater's Catalogue of the Lygaeidae of the World (1964) lists 20 subfamilies. He includes about 480 genera and nearly 2,400 species in the family, and many new gen- era and species have been proposed since 1964. We provide cytological data for 12 subfamilies; a total of 131 genera and 330 species are discussed here. Unfortunately, no specimens were available to represent several small subfamilies nor any member of the family Idiostolidae, which is primi- tive to the Lygaeidae. Some crucial gen- era and species in the studied subfamilies remain unobserved, and the nearly total lack of material from Australia and South America and rarity of material from Asia and the Pacific Islands (except Hawaii) all indicate that much additional work is required if the Lygaeidae are to be well known cytologically. Although this study represents a great increase in our cytological knowledge, only about 10% of the described species have been studied. Obviously, the conclusions that may be reached are limited. It should also be noted that analysis of the observed cytological facts about the Lygaeidae must depend heavily on what is known about other groups of Heteroptera, and few fam- ilies have been as well studied as are the lygaeids (see Ueshima, 1979, for a sum- mary of the cytology of the Heteroptera). However, patterns have emerged that can usefully be discussed. While cytological information has often been used as a basis for phylogenetic work on groups of organisms, exclusive use of gross data has sometimes resulted in un- likely conclusions. Cytological data must be used in the same way as more tradi- tional morphological data, and the same rules of analysis apply. Phylogenetic stud- ies require that unique characters be used to assemble nesting sets of holophyletic groups, that is, groups that contain all descendants of their most recent ancestor (Ashlock, 1971, 1972, 1974). Unfortunate- ly, no cytological characters are unique either to the family as a whole or to any group within the family. Characters that 780 The University of Kansas Science Bulletin seem to be significant are discussed below in light of these phylogenetic principles. HoloJ{inetic Chromosomes Heteroptera are peculiar in that their chromosomes have a diffuse or holocentric centromere, which results in the highly condensed, round configurations of these chromosomes during division (Ueshima, 1979). The Homoptera having the same kind of chromosomes, cytological evi- dence can be added to the great body of morphological evidence that the Heterop- tera and the Homoptera are closely re- lated. These chromosomes are not unique to the order Hemiptera (sensu lato), for similar chromosomes are found in the Odonata and Lepidoptera in the insects and in some sedges among the plants (Ueshima, 1979). Chromosome Number Chromosome number alone is not a useful phylogenetic indicator. All morpho- logical and behavioral features of chromo- somes as well as the noncytological char- acters of groups must also be considered if significant results are to be obtained. When Southwood and Leston (1959) de- rived the Berytidae from Cyminae, com- bining the two into a single family be- cause of a shared high diploid chromosome number (and two other dubious charac- ters), they ignored the fact that all Cymi- nae so far studied have an m-chromosome, while all Berytidae lack this structure. Proposal of a Cyminae-Berytidae relation- ship was unjustified, as has been carefully documented by Hamid (1975), even though his chromosomal data (1975:23, Table 2) are in many ways inaccurate. The significance of chromosome num- ber depends in part upon the ways in which chromosome numbers may change. Two courses of evolution seem most likely in these species: an increase in chromo- some number by fragmentation of auto- somes, and a decrease through fusion of autosomes. It is generally agreed that an increase in number through fragmentation occurs more often in organisms with holo- kinetic chromosomes (Schrader, 1974; Heizer, 1950; Schrader and Hughes- Schrader, 1956; Brown, 1961). Hughes- Schrader and Schrader (1961) induced breakage of chromosomes in some penta- tomids and found that the fragments be- have quite normally and perpetuate them- selves during the meiotic cycle. The possi- bility of fusion of two chromosomes in organisms with holokinetic chromosomes, which reduces the chromosome number by one, has been discussed by Schrader (1947) in the pentatomids, by Chickering and Bacorn (1933) for belostomatids, by Ueshima (\96bb) for the cimidids, and by Brown (1961) for the coccids. The male diploid chromosome comple- ments in the Lygaeidae so far known range from 10 to 30; the odd numbers 19, 25, 27, and 29 are not represented (Table 10), and 14 (12 + XY) and 16 (14 + XY) are very common and may be taken as two modal (or type) numbers in the family. The number 16, however, seems often to be derived from species with a chromosome number of 14. In the Orsilli- nae (Table 10), the Nysiini nearly all have 14 chromosomes, while the Metrar- gini nearly all have 16. The exception in the metrargines is the genus Dar winy sins, the most primitive genus of the tribe so far cytologically studied, which has a chro- mosome number of 14. Ashlock (unpubl.) believes that the Metrargini are derived from Nysiini; if so, the chromosome num- ber of 14 is primitive while the 16 chromo- somes found in the rest of the Metrargini is derived. The one Nysiini not having 14 chromosomes is Nysius tenellus Barber, which has 22. This species is not primi- tive in the genus, and the chromosome number of 22 must be derived from the 14 found in all other members of the Cytotaxonomy of Lygaeidae 781 genus investigated. In the Orsillini, the genus Orthotonus has species with both 14 and 16 chromosomes. In the Blissinae, the situation is even clearer because Slater and Ashlock (1976) have published a cla- distic analysis of the more primitive gen- era of the subfamily. Three of the more primitive genera (Blissus, Dimorphopter- us, and Geoblissus), containing 15 studied species, all uniformly have 14 chromo- somes. Members of more advanced gen- era have either 14 or 16 chromosomes, distributed so as to suggest that the change from 14 to 16 has occurred more than once. All species of these two subfamilies that have 14 chromosomes have one auto- some that is classified as extremely large, while those with more than 14 lack this large chromosome. Thus it seems likely that the large chromosome has fragmented in the process of evolution of the 16-chro- mosome species. In addition to Nysiits tenellus in the orsillines, Lygaeus simulus and Oncopeltus famelicus in the Lygaeinae and Pachygron- tha barberi in the Pachygronthinae have chromosome numbers far higher than is usual for their genera (Table 10). These species would seem to have undergone in- creases in chromosome number by frag- mentation. On the other hand, in the subfamily Rhyparochrominae, members of the tribes Drymini and the Myodochini commonly show a large number of chromosomes; less than half of the observed species showed lower chromosome numbers. In Drymini, 20 species show 20 (18 + XY), one species shows 18 (16 + XY) and three show 16 (14 + XY) (see Table 10). In the Myo- dochini, 30 species have 16 (14 + XY) and 12 species have 14 (12 + XY) chro- mosomes. In neither case is it clear wheth- er fusion (higher to lower numbers) or fragmentation (lower to higher) is re- sponsible for the range of numbers. Solu- tion of problems like these requires a cladistic analysis of the groups involved. Harrington (1976) has such an analysis completed for Myodochini. The highest chromosome numbers in the Lygaeidae are found in the Cymini (Cyminae) (28 and 30), with the (prob- ably) more primitive Ontiscini (22) and Ninini (22) not far behind. The only ninine exception is Ninus insignis (Stal), which has a chromosome number of 16. The Geocorinae show 16 to 20 chromo- somes, with the highest numbers in the highly derived genus Geocoris. The classi- fication of the Geocorinae is in especially poor condition from subfamily to species level, and requires much work before proper evaluation of cytological data may be attempted. The only members of the Rhyparochrominae with unusually high chromosome numbers are the Drymini already mentioned (16 to 21), with the majority of species at 20. The rhyparochromine tribe Lethaeini contains those lygaeids with the lowest chromosome numbers (11 to 13), partly due to the lack in this group of the Y chromosome. Since the closely related Antillocorini mostly have chromosome numbers of 14 (one species is 16) it seems probable that the lower numbers in the Lethaeini are in part due to fusion. Chromosome Size Lygaeids have relatively large chromo- somes compared to those found in such other heteropteran families as the Cimi- cidae. But even with these large chromo- somes, members of four subfamilies have one exceptionally large autosome pair. Of these the Henestarinae and Chauliopinae are known cytologically from single spe- cies. In the Orsillinae and Blissinae, the extremely large chromosome is found in all but a few species with a chromosome number of 14. Species with a higher number (usually 16) lack the exceptional chromosome. For this reason, we believe 782 Orsillinae &,. Darwinysius marginalis The University of Kansas Science Bulletin 12 34567 89 10 1 m I Q. Glyptonysius hylaeus (2, Neseis hiloensis approximata - E.Maui Q. Neseis hiloensis approximata - W.Maui Nysius abnormis I Nysius tenellus P\ Hudsona anceps h. Ortholomus arphnoides 1 Ortholomus nevadensis ft ft lit t t t I I I I f • • I t I t I t f I t Itllllll I I III! f I Fig. 131. Relative size differences of chromosomes in named species of Orsillinae. Cytotaxonomy of Lygaeidae 783 132 Lygaeinae 2 0- 10- X> E 3 C 7 8 11 haploid number 133 Orsillinae 30- 20- E 3 C o-1 n 7 8 11 haploid number 134 Cyminae £ 5- XI E 3 C J a 8 11 14 15 haploid number 135 Drymini 20- 10- xi S 3 C 8 9 10 11 haploid number 136 Myodochini 30- 20- XI E 3 C 6 7 8 haploid number Fie. 132-136. Distribution pattern of chromosome numbers in named subfamilies and tribes of Lygaeidae. Fig. 132. Lygaeinae. Fig. 133. Orsillinae. Fig. 134. Cyminae. Fig. 135. Drymini. Fig. 135. Myodochini. that the change in chromosome number from 14 to 16 in these two subfamilies took place by fragmentation of the large chro- mosome. One exception, Ischnodemus no- tandus (Blissinae) (Fig. 47), has a chro- mosome number of 18, but retains the extra-large chromosome. The remaining exceptions are found in two of the four species of Ortholomus studied (O. ar- phnoides, Figs. 26, 131h; O. scolopax), which have a chromosome number of 16 while retaining the large autosome found in the other two species studied, both of which are 14-chromosome species. If this increased chromosome number came about by fragmentation, it was of autosomes other than the exceptionally large one. Ashlock (1967) suggested that Orsil- linae and Blissinae are closely related. Even though evidence is not particularly strong (it is based mostly on primitive characters), his opinion was supported by Stys (1973). That both subfamilies have the exceptionally large chromosome may support the hypothesis because the large chromosome is unknown outside of the Lygaeidae in the Heteroptera and is as close to a synapomorphous character as we have found in this study. The one species each in the Henestarinae and es- pecially the Chauliopinae with the excep- tional chromosome is difficult to explain and weakens the Orsillinae-Blissinae hy- pothesis. The origin of the large chromo- some may have been the fusion of two autosomes, and there is no reason to be- lieve that this must be a unique event. The Sex Chromosome Mechanism The sex chromosome mechanism in the 784 The University of Kansas Science Bulletin Lygaeidae is fairly uniform. In the 330 species investigated, 296 haxe XX females and XY males, while the remaining 34 species are either XX-XO or have a com- pound X chromosome mechanism. One species has a compound Y. There is no doubt that the XX-XY mechanism is primitive in the Lygaeidae. Ueshima (1979) has suggested that the XX-XO mechanism found in Gerromorpha is primitive in the Heteroptera, but that the terrestrial Heteroptera gained the Y chro- mosome early in their evolution. Thus, the XX-XO system found in most families of the Coreidae (except the primitive Hyo- cephalidae) and a few Lygaeidae is secon- darily derived. The XX-XO system is found in all members of the tribe Pachygronthini (Pachygronthinae) (9 species in 3 genera studied) except the one species of the genus Uttaris, which has the XY mechan- ism. Slater (1955) considered Uttaris to be the most primitive genus in its tribe. Significantly, all four species in four gen- era studied in the other tribe of the Pachygronthinae, the Teracriini, have the XY system. All 14 species in seven genera studied in the highly derived rhyparo- chromine tribe Lethaeinae (see Ashlock, 1964), are XO, but all of the Antillocorini studied (a more primitive, closely related tribe) are XY. Finally, the only other lygaeids known with the XO system are the three species studied in the genus Poeantws, members of the rhyparochro- mine tribe Rhyparochromini. The origin of multiple sex chromo- somes is somewhat more problematical. When these mechanisms evolve in such insects with monocentric centromeres as Orthoptera and the Diptera, the number of autosomes usually decreases as the num- ber of sex chromosomes increases (White, 1973). But in the Heteroptera no such relationship is evident (Schrader, 1947; Ueshima, 1966a, \966b). Troedsson (1944) and Schrader (1947) suggested that a sim- ple fragmentation of holokinetic sex chro- mosomes serves as the major source of the multiple sex chromosomes in the Heterop- tera. Hughes-Schrader and Schrader (1961) experimentally proved the sugges- tion by inducing fragmentation of the sex chromosomes with X-rays in some penta- tomids. Ueshima (1966a, 1966£) reported support for the hypothesis in relative sex chromosome size differences in closely related species with single and multiple X mechanisms in the Triatominae (Redu- viidae) and Cimicidae. Reduction in auto- some number does not seem to occur in lygaeids with multiple sex chromosomes (Table 10), and the origin of the multiple sex chromosomes through simple fragmen- tation of sex chromosomes may be safely assumed for the Lygaeidae. Multiple sex chromosomes are wide- spread in the Heteroptera, and show little pattern in the Lygaeidae. In the subfam- ily Lygaeinae, of the 25 species (12 gen- era) studied, only one, Arocatus suboeneus Montandon, has an X1X2Y system. All others, including Arocatus rusticus (Stal), are XY. Similarly in the Blissinae, one of the two species of Cavdarias studied has an X1X2Y system. All other blissines (37 species in 10 genera) are XY. In the Oxycareninae all Old World species stud- ied (4 in 10 genera) have X1X2Y, but the New World Crophius bohemani (Stal) is XY. The possible significance of this distribution of multiple X chromosomes cannot be determined until more species are investigated. Of all the species of Rhyparochrominae studied, only four have multiple X chro- mosome: Thylochromus, X1X2Y; Grapto- peltits, X1X2X3X4Y; Megalontus, X1X2Y; and Sphragisticus, X1X2X3Y. Only one lygaeid, Rhyparochomus (Panaorus) an- gustatiis (Montandon) (Rhyparochro- mini), has a multiple Y chromosome, XY1Y2. Cytotaxonomy of Lygaeidae 785 The examples of multiple sex chromo- somes in the Lygaeidae are too scattered to be of any taxonomic significance, except perhaps in the Oxycareninae. The m -chromosome The only feature of heteropteran cytol- ogy that is not found outside of the sub- order is the m-chromosome. Most Ly- gaeidae have this feature, as do members of the Colobathristidae, Largidae, Hyo- cephalidae, Stenocephalidae, Rhopalidae, Alydidae, and the Coreidae — all families in the Pentatomorpha. (For a discussion of the division of the Heteroptera into the infraorders Enicocephalomorpha, Dipso- coromorpha, Nepomorpha, Gerromorpha, Leptopodomorpha, Cimicomorpha, and Pentatomorpha, see Stys and Kerzhner, 1975.) Other pentatomorphs : the Penta- tomoidea, the Pyrrhocoridae, the Aradidae, and the Berytidae, lack the m-chromosome. The m-chromosome, then, might be used as a synapomorphous character to group the families that have it into a single holo- phyletic group. However, as Ueshima (1979) has reported, most families of fully aquatic Hemiptera (the Nepomorpha) as well as the Saldidae (Leptopodomorpha) also have m-chromosomes. On the other hand, these chromosomes are absent from all studied Gerromorpha and Cimico- morpha. Unfortunately, the phyletic rela- tionships of the various infraorders are not established, and assessment is complicated by indaequate cytological information in the Enicocephalomorpha and Dipsocoro- morpha. It seems clear that the m- chromosome evolved fairly early in the evolution of the Heteroptera and has subsequently been lost several times. Thus, while there probably does exist a holo- phyletic group marked by the first ap- pearance of the m-chromosome, subse- quent losses make delimitation of the group impossible. In the family Lygaeidae, all members of the subfamily Lygaeinae studied (25 species in 12 genera) and all Oxycarininae (5 species in 3 genera) lack the m-chromo- some. This lack may corroborate the sug- gestion by Ashlock (1957) based upon the structure of the aedaegus, that these two subfamilies are related, a suggestion that has been otherwise uncorroborated. How- ever, the m-chromosome is also missing in two species of Rhyparochrominae: Tro- postethus holosericus (Scholtz), one of six species of Antillocorini studied in four genera, and Targarema stall B.-White, the only targaremine studied. Clearly, loss of the m-chromosome in the Lygaeinae and Oxycareninae is not an isolated event in the family, and the chromosomal evidence for a relationship between the two sub- families Lygaeinae and Oxycareninae is not very strong. Metuphase Position of the Sex a n d m -ch ro m oso m es The positions that chromosomes in meiosis take on the equatorial plate during metaphase is reasonably constant for given species. Generally, at metaphase the auto- somes form a ring and the sex chromo- somes locate in the center of the ring. A distinguishing feature of the m-chromo- some, in addition to negative heteropyc- nosis and the fact that the two m-chromo- somes do not touch during metaphase, is their location in the center of the auto- somal ring with the sex chromosomes during at least one stage of meiosis. Table 9 summarizes the position data we have found in the Lygaeidae. Groups in which the sex and m-chromosomes both locate centrally during metaphase I and metaphase II are the Lygaeinae (no m), the Metrargini of the Orsillinae, the Cy- mini of the Cyminae, the Blissinae, the Henestarinae, the Oxycareninae (no m), the Pachygronthini of the Pachygronthi- nae (no Y except Uttaris), the Hetero- gastrinae, and in the Rhyparochrominae, 786 The University of Kansas Science Bulletin the Lethaeini (except Lethaeus) (no Y), the Ozophorini, the genus Cligenes of the Antillocorini, the Drymini, the Stygno- corini, and the Rhyparochromini (except Peritrechus and Poeantius). Nearly as commonly in the Lygaeidae, the sex and m-chromosomes are central during metaphase I, but during metaphase II, the m-chromosomes are peripheral with the autosomes, and the sex chromosomes alone occupy the center of the ring. This condition is found in the Nysiini and Orsillini of the Orsillinae, the Ontiscini and Ninini of the Cyminae, the Geocori- nae, the Teracriini of the Pachygronthi- nae, the unplaced genus Meschia, and in Table 9. Summary of the characteristics of chromosome cytology in the Lygaeidae (absence of m-pair, — ; presence of m-pair, -\-\ central position, c; peripheral position, p). Taxon Lygaeinae Orsillinae Metrargini Nysiini Orsillini [schnorhynchinae Caprluobia ... Kleidocerys ... Pylorgus Cyminae Cymini Ontiscini Ninini Chauliopinae Blissinae Henestarinae Geocorinae Geocorini Oxycareninae Pachygronthinae Pachygronthini . Uttaris Teracriini Heterogastrinae Rhyparochrominae Plinthisini Lethaeini Lethaeus Ozophorini Antillocorini Antillocoris ... Botocudo Cligenes Targaremini Drymini Stygnocorini Cleradini Myodochini Udeocorini Rhyparochromini Peritrechus ... Poeantis Gonianotini Incertae Sedis Meschia Suggested modal no. m-pair Metaphase I ~X Y~~ Metaphase II ~X Y m" 14(12 + XY) — 16(14 + XY) 14(12 + XY) 14(12 + XY) 14(12 + XY) + + + + ? + ? + ? + 16(14 + XY) + 14(12 + XY) + 14(12 + XY) + 20(18 + XY) ? + 16(14 + XY) - (multiple X) 13(12 + XO) + 14(12 + XY) + 14(12 +XY) + ? + 16(14 +XY) + 13(12 + XO) + ? + 14(12 + XY) + 20( 18 -f-XY) 16(14 + XY) 5 14(12 + XY) 13(12 + XO) _ ? + + + + 4- + c c c- c c c c c c c c p c c c c c p p p c c c c p p c c c p p c c c c c c c c c c c c c c c c p c c c c c p c c c c c c c c c c c c c c c c c c c c c c c p c c c c c c c — c c — c c c c c c c C C C C C p C C c c c c c c c c c p c — c c — c p — c c — c c c c c c c c c p c c c c c p c c c c c c c c c p c — c c — c c c c c c c c c c c c c c c c c p c c c c c p c c c c c p c c c c c c c c c c c p c — c c — c c c c c c p 4- Cytotaxonomy of Lygaeidae 787 the Rhyparochrominae, the Plinthisini, Cleridini, Myodochini, Peritrechits and Poeantis of the Rhyparochromini, and Gonianotini. A few thoroughly unusual departures from these two patterns are worth noting. In the genus Lethaeus (Lethaeini, Rhy- parochrominae), the X chromosome is peripheral at metaphase I. In genera An- tillocoris and Botocudo (Antillocorini, Rhyparochrominae), the species investi- gated have the m-chromosome peripheral at metaphase I and central at metaphase II. The most peculiar situation is in the subfamily Ischnorhynchinae. The chro- mosomal evidence is ambiguous, but may corroborate a suggestion of Ashlock and Scudder (1966), in a revision of the isch- norhynchine genus Neocrompus, that the genus Kleidocerys (the type genus) is so unlike other genera of the subfamily that the subfamily probably is polyphyletic. At metaphase I, Kleidocerys and Caprhiobia both have the X and Y chromosomes pe- ripheral and the m-chromosomes central. In Pylorgus, only the X is peripheral and the Y and the m are central. At metaphase II, however, the X and Y chromosomes in Kleidocerys are central and the m is peripheral. In the other two genera, the X, Y, and m are all central. More data in this group is an obvious desideratum. In general, the positions taken by the X, Y, and m-chromosomes are difficult to evaluate. The large number of Hawaiian Orsil- linae reported upon herein is the result of an attempt (P.D.A.) to test the sub- species concept as it applies to insular populations. Two species of endemic me- trargine Orsillinae, Neseis hiloensis (Per- kins) and N. nitida (B.-White), live on the native tree Pipturus, and each has a different subspecies on most of the major islands (two each on the island of Ha- waii). Tabulation (Table 1) of the rela- tive sizes of chromosomes in the genus Neseis shows wide variation. Interesting- ly, chromosomal size variation among the subspecies of N. hiloensis is of about the same magnitude as among the various full species in this Hawaiian genus, while sub- species of N. nitida all have the same chromosomal size. No conclusions can be drawn without hybridization experiments. Several other genera have been simi- larly tabulated (Tables 2-8) and show similar variations between species. The rhyparochromine tribe Myodochini has just been reclassified (Harrington, 1976), and in this work, several species we list in the genus Pachybrachins (Table 8) will be transferred to new genera. Species and Subspecies Discrimination The most significant cytological work that can be done at the species level is to observe the behavior of chromosomes in hybrids of closely related forms. Any dis- ruption in the normal processes of chro- mosomal division is excellent evidence that reproductive isolation has been achieved. Leonard (1966), working with five forms of the Bhssus leucopterus complex in the eastern United States, found in two of his crosses a metaphase heteromorphic pair, involving the extra large autosomes, which bridged at anaphase. Ueshima (1966b) has done extensive similar work in the Cimicidae. While a breakdown in the meiotic process is excellent evidence that the parents of the hybrids are reproduc- tively isolated, it must be remembered that the opposite is not true, and normal behavior of chromosomes in hybrids is not in itself proof that the parents are of the same species. Reproductive isolation can involve behavioral and ecological factors as well, which may be bypassed in the laboratory. Chromosome morphology and number can provide evidence that two similar populations actually represent different 788 The University of Kansas Science Bulletin species. Specimens of two populations of the genus Cavelarius (Blissinae) collected within a few feet of one another in north- ern Thailand, of which one was entirely long-winged while the other was mostly micropterous, proved to be separate species (Slater et al., 1969). C. illustris Distant, the species with wing polymorphism, also has a multiple X chromosome, while the other species, C. minor Slater and Miya- moto, has the normal single X chromo- some. In the Hawaiian Orsillinae, one of the more interesting findings is a single specimen of what was thought to be Neseis hiloensis approximate, which differs from all other specimens of the genus in that it has an additional autosome pair. Careful study of the specimen showed that it differs from typical specimens of N. h. approximata in its pronotal cicatrices, which are pale brown rather than black. Later attempts to collect this exceptional form at the original site of the Kaualewe- lewe-Puu Kukui trail, 3,000 ft.. 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Studies on chromosomes, I: The behavior of the idiochromosomes in Hemip- tera. J. Exp. Zool. 2:371-405. . 1905£. Studies on chromosomes, II: The paired microchromosomes, idiochromosomes and heteropyenotic chromosomes in Hemiptera. J. Exp. Zool. 2:507-545. . 1909. Studies on chromosomes, IV: The "accessory" chromosome in Syromastes and Pyr- rhocoris with a comparative review of the types of sexual differences of the chromosome group. J. Exp. Zool. 6:69-99. . 1912. Studies on chromosomes, VIII: Ob- servations on the maturation phenomenon in certain Hemiptera and other forms, etc. J. Exp. Zool. 13:345-431. Wolfe, S. L., and B. John. 1965. The organization and ultrastructure of male meiotic chromosomes in Oncopeltus jasciatus. Chromosoma 17:95-103. Yosida, T. 1944. Researches on the chromosomes of twenty species in the heteropterous insects. Igaku and Seibutsugaku 5:729-732. 790 The University of Kansas Science Bulletin . 1946. A chromosomal survey in 20 species the morphology of sex-chromosome (I). La of heteropteran insects, with special reference to Kromosoma (Scnshokutai) 2:57-63. Cytotaxonomy of Lygaeidae 791 p5 NO O ON CN ,— 1 C3N no ON NO o ON CN ON O ON <3 O ON in NO ON C <3 in tN ro on u -a a -J-* in in ON in o >; 43 I_H H fN - ON 2 ro i — i -H CM «1 in on "4- „ rt on in on — ON „ no ^g oo ON -T3 *~ H ■^~ in ON '—' ON na, 19= ler, 193 ichow, V) fab e bi E oi rt bb E o 43 "3 rt fab - E s e o 43 ti E ti E ti E ti £ ^ be C rt u ti E m rt ti E rt E t* E C o> u» - 43 o u „ O „ C „ 43 ^ ^ Ut C iT rt 43 - •-t-l 0- "S X. rt 1m 1-. o _2 >-■ o o 1-1 d rt i- c rt l/> c *-* " 0J i-. 43 43 43 o 43 o> OO o O rt 43 P- $ u 00 45 i!£ ID 43 43 43 43 2 £ 43 43 s rt 43 soii J3 5j 4J rt £ IU o c "H |3 3, rt X +++++++++J++++++++++++++++++++++ NONONONONONONONONO»— "NONONONONONONONONO^Ht^t^r^r^NONONONONONONONO X ^ r1 i^1 r^ n n i's A + + + + E E £ E + + + + in in no no c u o u o o o c -r XXXXXXXXXXXXXXXXXXXXXX >H>H>H>H>H>H>H>H>-. 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S be g D < bo b D < rt 73 »- o Q -* be -G ' a < -c" W (/1 R ^3 R R R ft. «i v. bo .ft o C <3 s 5 ■ S 5 -5 -a ^^^S;^fe^fe:ie;^^^<:^^^^^fe:^ R OOOOO bo •5 >, S 3S j> o g> 0 o* o" d £ >- x +++++++++++++++++++++++++++++++++++++ + +++++++++++++++++++++++++++++++++++++ + X + < D n rt a: rt u. »5 ft. o X X C J3 Z o Cytotaxonomy of Lygaeidae 793 o a [3 3, "^3 s R O - n ■< H "3" so ON ■q- os — < fN - rr) w. •— ' u 7 ^ S™ OS irs c tc OS - v_ u, r <£i u cj U cj c -c x X- X: -r Os s - C c c ca "3 U u x x L, — u — U X h x c-, x £ j:x j= TT **■ OS OS ~H ro ro CO ro r—l 4J o-a ro T3 irs" so l~-T "g SO 2: tN l_ tsi rsi (si 5 ir OS ca <>*>,><>->->H>H>*>H>H>H>H>H>.>N>.>«>H>H>H>«>M><>->H>«>H xxxxxxxxxx xxxxxxxxxxxxxxxxxx ++++++++++++++++++++++++++++ EEEEESEE£EEES££££EEE£ESEEE££ ++++++++++++++++++++++++++++ >_>-,>-,>->-><>-, r« >" X X X X X X X X X +++++++ + + EEEEEEE E £ +++++++ + + in so i/-\ irs irs so i/-\ ITS l/"\ to ^^Pm^Jm^^Jm^hJm^^^^^Jw^^Jw^^^^^,^^^^ > > >• >- >• >H >- r« xxxxxxxxxxxxxxxxxxxxxxxxxxxx X X X X X X X X ++++++++++++++++++++++++++++ + + + + + + + + NM(Sl(s|tN(sltsi(s|tN(sllNN(s|(NM(NNCsl(NNCO(NN(s)N(N(Sl rsj rr rxi rxi t r-j rsi (N TT-TT-TTTTtrTT,rTTT'rn'T^r^_,3-(N(N^*Tf^",1"^",r f vo rr T so -r TT I" < < < < < < y, < < < < .2 'S ?0 I — 1- u ro P ^ o ^1 p '. ~> s i o « S Si 5 a 6* « ^-^ ^-H4 ^^f ^^Hl ^"H ^-H) r> r> 1j o DC a c ra _o X < X ca ca pa u: o ca x u CO X t» S •« ^ .*< « R >o U 60 C 5 § p.- ^ § i •. *j o i ** w !i r>r>r>^r>^r>^r>r>^^ ^> "< £■ ft s'o ^ r> ^ K, R <-. « s R O u T ca CQ -. 1 B R 01. ft < z DC U z r" ^ z F u oo mi R -a 3 fti£ ■S si iodd o o ft, •» « . 794 The University of Kansas Science Bulletin QO NO on o o\ c u 04 ON {N E ON e ^< — o C U a W. c s I 5 |« c "^ " ON -g i_T - cs ; ^2 o C ON M E 3 O Ml O E C j^ _H 0~ -±! in E >- cj re 3 >~ wo"irt1-r301-1-1- U — ^- J O •— « , ■" '^h O M-i <_. u o o u E PO bi E U 4J O *-> o £ t-H C C3 NO E r° SJ1 pn E "O vo vo \£> SO V£> VO VO VO so ro ON ON r^i ON ON ON ■ — 1 — 1 ^^ * — ■ "—' !~.f „ n hn ,. „ ^ — U* t_ Uh i— a rt rt rt r3 o 9J a C QJ C c C flj o 4J u *> O o U o QJ o c "2 a >H >H >H >H >< >H >- X X X X X X X + + + + + + + X + >- >< >> ^ X X X X + + + + >- >* >< XXX + + + X >- >H >- >H X X X X X X xxxxxxxxx + ++++ ++ +++++++++ +++++++ IT\ IT\ IT\ IT\ \T\ IT\ IT\ + ++++ +++ + + + + + + + OS On On On no NO NO +++++++++ l/NiniAI/Nl^mlOlAUN "^3 a o w « < o >H >H JH >H X X X X + + 4- + M (N IN (N 1- 1- *t" T- X + X + oc CM O X + NO OO CM X X + + OO NO r^ rsi O 3C < < < < W !/)7) CO DDD ~ — o _ D — ■% M ■* r r Ih . c c <-i— u-> *-^- -: - c C8 < < >- >H XXX + + + OO 30 NO M M (Nl O O OO ^ ^ N < < E-s< > X X + + + + + (N (N N « (N IN N >0 fN| (N IN « c -a a h c C : XXXXXXXXX + + + + + + + + + + -r rsirsi(N(NrN| ■-> s s j^> ti S *> C ^ "s -2 Nj ~"3 ^ ? -2 © S % •£ - © - 5 '< ^ ^ bo Ui JS c 3 H B •5 o O < Z O 3 o s _ „ c°2 c c i w j: 3 I 2? 5 o S 5 5 O .j.«o| - K Z Sow ^ i— i § '3 -2-2 -2 S> w 2 a ~ s o s S — R R NJ O pq R S ^* ■ • S * C o -a c - c o ^2 S W m 3 «, •S ^ o" r* vt o o — cq cq cq Cytotaxonomy of Lygaeidae 795 — a X "S3 a c R o w pa < - o V> rS CO c: — rv) ■*• -<3- -3- iC u. u iZ IZ '£, se _C J= -C -C -C -= — VO o ON — ' ^H n ^r "^ - o CN u. ~~ 4J T l/^ ^ vo r^ c ^r- ^r ^ ^3- Efl tac be J- tc tc - U, Uh bfl EX X O O Cj u o 9J C o U |j L( u ^1 i— i_ i— — u, — — — QJ U (J V 9J 2 LI r: -C -C X _r jz: X pC _c _c ™ _ T -T ON -" »— ' 1 — 1 1- u U CJ • ;j — X O ^ • — ' CM C rn C TJ- l/^ -r u~: U^ J3 ITS n w. tc M be tx 0 M Ph PL, Ph P- Ph U Ih Ph U ij ij ;, 4j O u V h >h ;h XXX >< >H X X >H >H >H r^.>H X X X X X +++++++++ + + + - xxxxxxxxxxxxxxxxxxxxx +++++++++++++++++++++ X + +++++++ ++++++++++++++ + lA^ir. ir\mini/Nmvoi^vcvoo\omi/iNiri\ovciAiA\cmi^>^ < < co co D D < CO D < "5 to CO c c .y U U co t- < CO D Pi »J — CO < « J < < co JZ, H co co _ _o CO Ph S o 0 n „ _ ■>* *■ ij ^ y> vi "t: c v. <. 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